[If you are looking for a quick answer, jump here.]

Yesterday morning was probably one of my least favorite in recent memory.  I arranged to take the day off to go shopping with my wife, but I had to check-in to make sure everything was okay at the office.  I checked my email from home and found that there were suddenly two issues reported on my project that was scheduled for an update in production that night.

Needless to say I had to address the problems.  It turns out that neither were more than a five minute fix in each case.  However, I got slammed with an unrelated issue on my laptop that brought me down to a crawl.  At one moment I was reproducing the error the users reported, the next I made the code change and tried to run the web application again and got a totally unrelated error: "asp.net ajax client-side framework failed to load".

I searched the web and found lots of hits, but wasn't having any luck.  Most of them involved deployment to another server.  In my case, AJAX just suddenly stopped working on my box.  I was in dire straits.  I needed to get the fix to the customers as soon as possible, and I had no way to confirm it.

I described the problem to my wife, and I discovered yet another reason I can be certain I married the right woman.  She simply said to me, "Why don't you try it on your other computer?"  Duh!

I had upgraded a few months back from one laptop to another.  So, I still had the old laptop laying around.  I just needed to get the project updated from svn.  After that I was able to make the fix, test and deploy. 

Resolution However, I still needed to figure out what was going on with my new machine.  I left it alone yesterday and picked it back up again this morning.  I gave up on my Google search temporarily and found .Net 3.5 SP1 in my Control Panel - Add/Remove Programs.  I clicked Change... and was relieved to see a "Repair" option.

With bated breath I waited for Windows to complete the repair.  After a few minutes of reading blogs in Google Reader, I saw that the repair was complete.  Now for the test.  I ran my web application and all of the Ajax errors disappeared. 

Perhaps this was coincidental; who knows.  I suppose I could go through my logs, but I'm back in business and that is good enough for me.  Of course, this doesn't explain how Ajax got broken in the first place.

posted on Thursday, December 11, 2008 10:13 AM
Filed Under [ .Net ASP.Net AJAX ]

Comments

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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by S
on 12/17/2008 11:20 PM
Thanks very much for posting this - saved me lots of time, and I may not have ever thought to run a repair on a service pack. An update to 3.5SP1 also stopped my web-server delivering Ajax as well.

There are a lot of Hotfixes floating about, but it might be related to:
http://support.microsoft.com/?kbid=948609
or
http://support.microsoft.com/?kbid=948610

which were applied about the time my Ajax stopped working.
It seems to be a busy Christmas as Redmond,
Anyhow, thanks again
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Jethro
on 3/4/2009 2:28 AM
I had the same problem. It seems that if the system date is not corrent it gives this error. Strange one hey. Anyway.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Bob Gear
on 3/13/2009 9:06 AM
Thanks for posting this solution. Fo no reason I can think of Ajax just died and these were the exact symptoms.

I have been *hours* knocking my head agaist the wall with this.

For the record the things I tried (unsuccessfully) were:
Checking all my code up to and including reverting to last night's commit
Restarting Visual Studio
Full Rebuild
Restart IIS services

I would never have thought of reparing the framework.

This is one for the GOOHF file.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Joseph
on 7/22/2009 11:23 AM
I was able to solve the issue simply by clearing the cache (CTRL-F5)
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Andy
on 7/28/2009 11:53 AM
Just tried developing an ajax site on my new computer; this solution worked! Don't know how long it was broken since I don't do much web development.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Ross
on 7/31/2009 9:31 AM
I'm afraid repairing the .Net 3.5 sp1 on my Vista computer and on my W2K8 Server didn't resolve this issue.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Lynn Demarest
on 10/17/2009 10:23 AM
I THINK had a BASE statement in my master page that when the PORT changed in Visual Studio, caused the library not to be found. In any case, correcting the port # to show the new port fixed the issue.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Yuriy
on 10/22/2009 11:57 AM
Or sometimes the problem is in Web.Config :) http://codecorner.galanter.net/2009/07/08/correcting-aspnet-ajax-client-side-framework-failed-to-load-error/
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Mark Costello
on 12/16/2009 10:24 AM
Hi folks - I ran into the issue where the ajax update panels stopped working for no apparent reason on a production server. I had to uninstall the service pack fully, then uninstall the ajax extensions - this breaks the site fully until you reinstall the extensions. Then download and install the SP (not using the windows updater) and install the KB updates seperatly
Hope this helps
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Purnima
on 1/4/2010 10:13 PM
Thanks. It resolved my problem.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Abduallah
on 2/12/2010 5:17 PM
thnx a lot really thanks :)
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Eduardo Xavier
on 7/13/2010 9:54 AM
I tried your approach and didn't work. So I remember I've installed a URL Rewrite software for wordpress on my server. I uninstall it and we're working now. Anyway.. say hi to your wife!! Sometime I share such problems with my wife, she is not computer professional but has wisdom different vision of things!! :)
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Archer
on 9/19/2010 4:16 PM
I also experienced this problem now but when I clean the cache (from joseph) then I solve the problem. I think this is because the cache is using the old version of the framework before the update.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by kannankeril
on 10/21/2010 4:15 PM
Thanks for the tip!

I have VS2010 and .NET 4.0 and ran across the same problem. Repairing 'MS .NET Framework 4 Client Profile' and 'MS .NET Framework 4 Extended' did the trick.

I would never have thought to do that without coming across your entry.
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Eron
on 10/5/2011 11:30 AM
very good...
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Vishalrd
on 7/27/2012 2:24 AM
Hello

i tried everything..but i am still getting same error..i change config file and reinstall framework :(..no luck.. I am using VS2010 and AJAXtoolkit 4.0. I getting this error on NLB server. My application work fine on local app server but when i open link on client browser then it gives me error...any suggestion pls
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Vishal Dandge
on 7/30/2012 2:40 PM
Hello,

I am using Asp.net 4.0 and Ajax v4.0. I am using AJAXToolKit for quick search functionality..I am getting ‘Sys’ is undefined or ASP.NET Ajax client-side framework failed to load in a ASP .NET 4.0 website..When i run my appliction on local server then everything work fine but when i access my application from NLB client server then i get this error..I check both application server IIS setting, Machin.config, Web.config..all are identical..even i try to make changes in web.config file like putting handlers, etc.. but no luck. i assume in .net4.0 there no need to change in web.config as it is already taken care by Visual Studio...i gone through many blogs and tried all combination but no luck..:(..even i restall my framework on both application..rebooted many times...pls let me know if you can help me..fast response is appriciated..thanks
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by jack straw
on 8/14/2012 7:47 AM
I tried repairing both 'MS .NET Framework 4 Client Profile' and 'MS.NET Framework 4 Extended'...still no luck. When commenting my forms auth out of the web.config, and re-running it worked. Then I am able to uncomment the forms auth, and have everything work as normal again. Very odd... I believe it has something to do with browser caching, as it all started for me when I cleared my cache while still debugging...
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# re: Resolving "asp.net ajax client-side framework failed to load"
posted by Ashish B
on 4/4/2015 12:37 AM
Try changing the application pool of your application from application settings.also try putting an empty "Webresource.axd" file in root folder of your allpication.

read this
http://www.telerik.com/help/aspnet-ajax/introduction-troubleshooting-production-server.html

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