There was such problem but we fixed it in Q3 release. Could you please verify that you are using Q3 or later .dlls. Also could you please specify what culture you are using, because if in your culture "," is used as decimal separator you have to press "," on the keyboard.
If the above doesn't help, could you send me a sample project where I can reproduce the issue because it is working fine at my side. Maybe some property or custom code is causing the problem.
the Telerik team