Oh there's a reason it unloads the nvidia_drv.o module (the "nvidia" driver):
(EE) NVIDIA(0): Failed to initialize the NVIDIA kernel module!
(EE) NVIDIA(0): *** Aborting ***
Make sure the kernel module is loaded (do an /sbin/modprobe nvidia
as root before you startx as your normal user), and see if you get this again.
If you do, then make sure your BIOS is configured correctly -- "PnP OS" (or whatever your BIOS calls it) has to be off, and "Assign IRQ to VGA" has to be on.
If modprobe'ing the kernel module makes it work, then you have to either add an alias to /etc/modules.conf, or add a line /sbin/modprobe nvidia
to /etc/rc.modules (or some similar file, I don't remember which file Debian uses offhand).