Hi Tobias,
I assume that the
RadCompression module is enabled in your project. In that case, the problem probably origins from one known issue - if you are using .NET 4.0, event handlers might not be raised in a default document in IIS 7 or IIS 7.5 Integrated Mode. The solution for this problem is described in details in our help article
here.
Regards,
Nencho
the Telerik team
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