When you post the same question in the forums and in a support ticket, please notify us about this in the support ticket. Otherwise we may end up with two support officers replying to the same question twice, which is an overhead for us. Thank you.
No to your inquiry: this problem has been fixed for Q1 2009 SP1 (version 2009.1.402), please upgrade.
Note that the decimal separator of the textbox' culture (comma in your case) must match the
decimal separator of the selected keyboard layout.
For example, if the textbox uses a comma as a decimal separator, and
your keyboard layout is US, the Del key will not work, because it will
output "." instead of "," and the textbox will not accept it.
the Telerik team