The version you are using is very old and has been released before these devices were available, so it is natural that there would be some problems between them. With newer versions we have taken care of a lot of bugs the iOS constantly introduces and the current version (Q2 2012) works well under iPad and iPhone. With Q2 2012 we also began the MetroTouch
initiative which is a skin that is designed for touch devices. Please also keep in mind that the .NET 2.0 and the "Classic" version of the RadControls for ASP suite are no longer supported. More information on the matter is available in this blog post
and this page
All that being said - the best course of action is to upgrade to the latest version - currently Q2 2012 (2012.2.607).
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