Could you, please, verify the version of the controls you are using, on our side this version : Telerik.Web.UI_2012_3_1016 works as expected and the issue no longer reproduces. You may also try downloading the Service Pack 1 and give it a try too.
In case the issue persists, it would be very helpful if you could open a support ticket and send us a sample application, which reproduces the issue with these versions, so that we could debug it locally.
the Telerik team
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