If when you open – at design time – a form in visual studio 2005 and raise exception: System.ComponentModel.Design. ExceptionCollection.

You can try to fix error with this tips:

Start a second VS2005, go to tools, the first option is ‘attach to process’.  The process is called devenv.exe.  For good measure, you could click on ‘attach to’ and make it report any sort of error, but managed code is what it comes up with, and what you want.

Now try to open the designer again, and the second VS2005 should break on the line th at is causing the error.  At least, that’s what happened to me when the IDE was both displaying an error dialog, and then crashing out.

Good luck.

Tips Source: msdn forum