Could you specify whether this behavior is reproduced in different browsers or only under specific one? In case you are using Ajax, please try to set the EnableAjaxSkinRendering
property of both RadListBoxes to True
If the above suggestion doesn't help or you are not using Ajax, please provide a live URL to your application so we could try to reproduce the problem on our side.
All the best,
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed