Project wont build because of problem in temp asp files?

Hi - I have a project - very simple - just a couple of master pages, a few .aspx files and a search component. When I try to build the project I get an error :
Error 2 Invalid expression term '.' d:\Users\me\AppData\Local\Temp\Temporary ASP.NET Files\mySite\3d0f527b\882f5c48\App_Web_n4vnipj3.0.cs
Now -there's no errors in my code. I have tried deleting the temporary ASP.NET files but the error always happens.
And - the site wont run under IIS either - it gives the same error - like the error is in the temp ASP.NET folder.
Any idea how to fix this?
Cheers.


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