glxinfo | grep direct => reboots my system, WTF?!

Per instructions on installed Beryl to Ubuntu Edgy (6.10)
https://help.ubuntu.com/community/BerylOnEdgy
I open a terminal and type
glxinfo | grep direct
and my Ubuntu 6.10 system (Gnome window manager) suddenly blanks the
screen and logs me out to the GDM login manager to log in again. What
the frick is going on with that? It seems quite bizarre that such a
terminal command would log out a user. My system has an nvidia
Geforce 7900 card with 256MB video ram, and I have installed the
native nvidia driver from nvidia.com All works fine except for that
command logging me out!

.