I tested the provided code but unfortunately I was not able to reproduce the problem. Since I have not analyzed the issue locally I can only assume what could be its possible reason.
Please, make sure that you have used the correct <!DOCTYPE> declaration because our controls are XHTML compliant and in order to make them function correctly you should not use quirksmode.
The needed declaration is the following one:
|<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
Also, make sure that there is no additional text between the declaration and the page's directives.
In case this does not help, please open a new support ticket and send me a sample, fully runnable reproduction project along with a detailed explanation and some screenshots of the problem. Once I receive it, I will do my best to help.
the Telerik team