The controls from the Telerik UI for ASP.NET AJAX suite are supported in IE browsers with version 7.0 and above. You can examine this sheet
Using the IE10 compatibility with the IE5 quirks causes the browser to use IE5 engine, therefore, due to the unsupported browser engine the control fails to work properly. I assume this is due to compatibility matters related to JS logic.
I suggest using an more recent browser engine, e.g., IE7 mode.
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