While working with Visual Studio 2008, I would constantly get exceptions thrown at me while working with any ASP.NET AJAX page. I also had no Intellisense when working with JavaScript which was a pain. I found an issue to the problem from Josh Berke on his blog here. It seems that there is a conflict with using a fingerprint reader while you are working with AJAX (they are somewhat related, aren't they?). You have to open up your processes (ALT + CTRL + DEL) and kill DPAgent.exe. Doing this immediately got everything working ... thanks Josh for the tip!