I tested the provided code in FF, IE6 and IE7 and could not reproduce the problem, please find my test page attached. I used the latest version of the RadControls for ASP.NET AJAX suite, namely 2008.2.723.20.
Could you please prepare and send us a simple running project, demonstrating the described problem?
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.