Start menu and task bar are freezing / blocked during backup


I use rdiff-backup with Keep for automatic backups. During the backups I can not use the start menu (k menu) - it does not react and the task bar and the whole panel at the bottom are blocked as well. The icons are fading, as if the system is crashed. After the end of the backup everything works fine again and all my clicks on the start menu and task bar are executed in high speed. lol!
Working with the system and all already opened applications is no problem during the backup. Alt-TAB is still working and the speed is ok too. So it seems to be no system crash.

Any idea?

Cheers Eisi

OpenSUSE 10.3
KDE 3.5
Athlon XP 2000

My problem is partly solved. If I switch to KDE Style for the start menu instead of the Suse style I have no problem. So the Suse style seems to be the problem.