We managed to reproduce a similar problem only with "Quirks" document mode. Could you please, verify that you are not running the page under such a mode or whether there is no anything else which differs your page from the demo?
Basically, the controls should work fine even with Doctype 4.0 - it is not officially supported, but behaves well in most scenarios.For our convenience I am attaching my test page here - I used 2012.3.1205 version of the controls as mentioned and test it under IE8, IE9, IE10 along with the above provided Doctype. You could see the video from my test here
Looking forward to hearing from you,
the Telerik team
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