ignored keyboard hit

[Daniel Barna]

Hello
Some times (mostly after workspace changing via Ctrl+Alt+Left or 
Ctrl+Alt+Right, but I could not exactly determine if this is regular) the 
first keyboard stroke is ignored, which is more than disturbing. 
This was exactly the reason why I gave up fvwm2, and tried xfce, 
but it seems now that this has the same problem. Or is the problem's root 
at a different level?
I am using XFCE 4.2, SuSE 9.3 and kdm as display manager.
Thanks
Daniel