the file cannot be processed because the code directory has not yet been built

hi all 
i get the following error and it has taken me nearly a day but not able to slove it.
Warning 16 C:\Users\mark.alphonso\documents\visual studio 2010\Projects\WebPortal\WebPortal\Management.aspx: ASP.NET runtime error: The file '/Site.master' cannot be processed because the code directory has not yet been built.
have tried restartign VS2010, closing all the pages and rebuilding it, deleting site.master from the solution and adding it to the solution again, but still no solution.

urgent help required.
regards,
mark
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