Check out bug  FDBK13913 on the MSDN Product Feedback Center.  I submitted this bug after trying to convert a VS 2003 web application to Whidbey Beta 1 using the built-in convert project wizard.  Because of the change from code-behind to code-beside, this project is incompatible with Whidbey if unchanged.  Yes, there are workarounds, and I used one, but I submitted this bug because that’s what it is, and The Web team is working on the bug now.  I’ve submitted some bugs that were duplicates, but this one was unique, so if I didn’t submit it, who knows if someone else would?