X/WindowManager: Mouse jumping around

[Reto <blackhole1@gmx.net>]

Hi again!

After the very good tip about the bug with "$REALSTARTUP", I have another 
problem with X or maybe even at all, I don't know:

When I startx the mouse jumps around wildly. It works for some seconds, 
then it hops around, also pressing buttons. This makes working impossible, 
of course :(
I have Debian Sid, a Logitech cordless Desktop, so a PS/2 mouse, which is 
configured in X as standard "configured" mouse on dev/psaux.
 Why does this happen and how can I fix it?
 Tnx in advance
  Karl