Hi Falk Wegener,
Yes, we believe that the described issue is addressed in our latest release. However, this may be a similar but different issue. Please, could you send us your application. This will allow us to investigate the issue and detail and provide you with accurate support.
I am looking forward to your reply.
the Telerik team
Q1’11 SP1 of RadControls for WinForms is available for download
; also available is the Q2'11 Roadmap
for Telerik Windows Forms controls.