Maybe try to add a file /etc/X11/xorg.conf (ask google, how it has to look), and in it set the driver "nvidia".
Make sure, the nouveau kernel driver is blacklisted. BTW: Is the proprietrary driver compatible with latest xserver-xorg again? Best regards Hans > Thanks to people for their helpful suggestions about installing the > proprietary driver (sorry it took so long to actually get it done: I had > some work in progress for a client, and didn't want to run a risk of ending > up without a working graphical desktop. That work ended yesterday, so this > is the first time it's felt safe to try the switch to the new driver.) > > Doc