I tried to reproduce your issue and it seems that the code works as expected on our side. I tried it with our latest official release Q1 2013 (2013.1.0220). Can you please take a look at the attached project and check if I missed something. If you can still reproduce the issue I will need some more information to better understand your scenario.
Which version of our binaries do you use? What is your OS and browser?
It will be best if you can send me your project or insulate the issue in a separate solution and send it to me. Looking forward to hear from you.
Pavel R. Pavlov
the Telerik team