We tested this scenario on multiple machines, but we are still unable to reproduce your problem. Please update your instance of Safari to the latest version and check if there are corrupted plugins that are causing the issue at hand.
I would suggest also checking again the screen capture that Dobromir attached in order to verify if the steps for reproducing the problem are followed correctly.
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