I tried to run Call Graph on my C# code from within Visual Studio 2003. ITune restarted IIS, and then various web parts in Sharepoint displayed the "cannot deserialize web part" error message, including the Windows Sharepoint Services homepage.gif icon in the upper right of the Team Web Site Home Page, the Web Part Page Title Bar on web part pages,and our custom web parts. The rest of the Home Page displays ok, including the home.gif, Quick Lauch, Announcements, Events, Links. Stop the Call Graph activity, and everything works again.
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