I\'ve been having this problem for a while now. I created a brand new winforms c# application in Visual Studio. I can usually launch it in debug mode once without a problem.
I added a web service/reference to my Web Server and then my Visual Studio went all crazy and wouldnt recoginze and custom controls or web services. The pages worked for the end users.. Just had access / recognition issues in VS.
I saw a few posts to remove cache files in C:\Users\gklein\AppData\Roaming\Microsoft\VisualStudio\10.0\ReflectedSchemas - I did that but it didnt work for me...
What did work was when i recompiled the web server, there was an error about access to C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\remedy\7642007a\c5be7720\App_WebReference file/folder...
My web server runs impersonating a global network user with elevated access rights...But they recently migrated my pc to a new domain where that user has no rights. The web site couldnt compile (as that user) on my pc. - Once I manually added that global network user as an admin on my pc... cleared cache and restarted VS.. IT WORKED!!!
hope my experience helps some else tooo