Upgrading a VS2010 web forms app to .net4

[Glen Harvy]

Hi, I have asked this question in the asp.net forums as well as stackoverflow without any success and I am hoping that someone could help me out. First of all I just changed my Target Framework from 2 to 4 in a asp.net web forms application that was working perfectly well in asp.net2 and now I have this problem. My post on asp.net has all the gory details but essentially I have created a new Web Forms application in VS2010 that targets .Net4. It runs fine in the developer web server - it should as there are no changes :-). I then add a reference to a dll that I have compiled for .Net4 and VS2010 freezes. When I use Task Manager to shut VS2010 down I get the following error messages. The message regarding the source file is not displayed until I run Task Manager to shut VS2010 down. For testing purposes, I removed that dll and added a reference to a commercial dll compiled that targets .Net2 with the same results. Can anyone suggest what I am doing wrong. Thanks - any and all suggestions appreciated .....