Do you recall the warning?  It was probably a Source Control issue, which you can safely ignore.

Were you able to rebuild the project?

If you search Google for the error you will find lots of information.  Here is one: http://forums.iis.net/thread/1305213.aspx

The solution suggests not using the default IIS server.  We actually develop on Windows Server 2003 and we do use IIS instead of the ASP.NET debug web server.