Item is not declared - suddenly: id = correct, all runat "server" items

 I suddenly (when reopening my project) have
AdRotator1 is not declared
txtSearch is not declared
menuLoggedIn , menuLoggedOut is not declared 
 errors in my project.

How is this possible? My id's are correct and everything runs @ "server".
I'm willing to give you the project, to let it see for yourself.

With friendly regards,
NicoJuicy

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