Sorry I should have stated this before but I am using MVC not webforms, but I did set these items in the webconfig pages section and still no joy, we are not using a web farm but we are using a professionally hosted dedicated server and the IT has made sure that all the keys are set right. This error comes up in a dialog during upload of the file bfore I post so during the ajax portion. Strangly it was working fine for quite a while.

Any help is appreciated 

thanks