I have a similar problem when the compiz 'reflection' effect is enabled.
I started having freezes upon using Karmic and turned of all compiz
effects at that time. I have since been enabling some effects and this
one seems to be the culprit.
It's not particularly important to me, but it is a bug.
Hmm- This bug is not keeping me up at night since I can switch to
Metacity before running Octave and prevent this problem, but in posting
this I was hoping that somebody who knows more about
Compiz/Octaviz/Octave/Nvidia Driver could direct this report to the
appropriate people. If you know a bit ab