Could not load the assembly 'App_Web_kle5twg3'. Make sure that it is compiled before accessing the page

I just upgraded to visual studio 10 from studio 2005,  i was using a 2.0 framework, but when I upgraded to VS 10 my framework was upgraded to 4.0.  The app works fine on my local machine but When i publish my app on the web server it returns the following msg:
Could not load the assembly 'App_Web_kle5twg3'. Make sure that it is compiled before accessing the page.
Please help ASAP.  I have been trying to fix this for 2 days.
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