vs_errorWhile developing a web application for a friend of mine, I ran into a Visual Studio error message I hadn’t seen before: Error connecting to undo manager of source file ‘D:DevelopmentSomeWeb ApplicationDefault.master.designer.cs’.

The error occured whenever I tried to start the (web) application in debug mode. The application did start OK after the error message though. Starting the application without debugging didn’t cause the error.
I closed the solution file I had opened, but that didn’t solve the  issue. Stopping the ASP.NET Development Server didn’t do anything either. I had to exit Visual Studio al together to get this error to go away.

I searched for this specific error, and saw it already occured in Visual Studio 2005 SP1. Scott Hanselman has a blog post on how he solved this issue. Now, in Visual Studio 2008, this error still seems to be in there…