Hello Max Kaplin,
Is in the RadFilter in a usercontrol loaded dynamically?
I assume the cause of the issue is that the usercontrol is not loaded properly and its scripts are lost.
Please examine this demo
to see how to load user controls dynamically.
I hope this helps.
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed