I know it is a bit tooo late to admit that I am still using Visual Studio .NET 2003 heavily on my projects. So yesterday I happened to open my first 2005 solution which is converted from 2003. Later on I decided to continue my work using my previous environment which is 2003. But nothing was working normal. I was unable to update web references, I could not debug my project and attach aspnet worker process to my debugger. And all the messages I get had no info in them like:
"Unable to attach the debugger" or "Unable to update the web reference.."
Obviously it had something to do with the framework version difference of the two environments.
I checked IIS and from the properties of my web site, under the ASP.NET tab, there it was! ASP.NET version was changed to 2.0 and although I was using 2003 environment, the settings on the IIS did not change. So 2003 had problems working with 2.0
That is what my hassle was all about