Has anybody else run into this particular problem with MS Office and SharePoint WSS?
What happens is a user tries to open a document on a SharePoint site, and even though the document isn't locked, it is opened as Read-Only.
I've tried some of the recommended fixes from various sites, including the one from Microsoft which says that it won't work for Sharepoint (but other users say it does), and they just don't work on my machine. I can't and don't want to try to do those fixes manually on the user's machines either, as some of them recommend reinstalling Office.
In desperation I tried to find out exactly what was going on, using RegMon from Sysinternals (now Microsoft Sysinternals).
What I found is that when a user clicks on a Document URL from the web, IE launches Excel using the OpenAsReadOnly shell command (by default).
By modifying the registry so that the command to Open as Read Only would essentially do the same thing as the regular Open command, I was able to workaround the situation, although for some users this was temporary - the next day something restored the settings back, and they had to run the registry hack again.
For anyone interested, I am on WinXP SP3, MS Office 2003 Standard Edition, with Compatibility Pack for the 2007 Office system (KB923505) installed.
Copy and paste the below into a text file and save as .REG:
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\Excel.Sheet.8\shell\OpenAsReadOnly\command]@="\"C:\\Program Files\\Microsoft Office\\OFFICE11\\EXCEL.EXE\" /e"
I've gotten in touch with Microsoft support and they have told me that his can occur when the HTTP OPTIONS message is being blocked somewhere between the server and the client.
The OPTIONS message is used to query the browser about WebDAV capabilities and whatnot, and it looks like Office sends this out when trying to open a file from a web site.
This article is extremely enlightening as to what goes on behind the scenes with Office/SharePoint.
Using NetMon, I was able to confirm that the OPTIONs message was being blocked, but as I do not have direct access to the infrastructure I am unable to verify if this is a software or hardware issue, although the MS tech guy did say that the F5 Big IP Load Balancer and Cisco Content Server Switch can cause the problem.