Unfortunately this seems like a bug related to RadScheduler when it is viewed under IE in 'Quirks' document mode. I have already logged an item for this issue in our PITS system and we will do our best to fix it. Here is the link to the PITS item: http://www.telerik.com/support/pits.aspx#/public/aspnet-ajax/12017
As a token of gratitude for reporting this issue to us, I have added some telerik points to your account.
the Telerik team
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