I hate to chime in on this but I'm using Debian as well. I had X working, the nVidia driver loaded, and everything was rocking but I couldn't get Neverwinter Nights working so I zapped my install to start afresh.. big mistake!

After a fresh 3.0r1 install, I compiled the 2.4.20 kernel and lastly downloaded and ran the nVidia driver (.run file) It worked as expected but after editing my XF86CONFIG-4 file I get the same errors as initially reported:

(EE) NVIDIA(0): Failed to initialize the NVIDIA kernel module!
(EE) NVIDIA(0): ***Aborting***
(EE) Screen(s) found, but none have a usable configuration.

Here's some background:
Hardware is 700MHz PIII, 128 MB RAM, nVidia TNT2 w/32MB
OS = Debian 3.0 (reproduced with stable and testing..)

changes I made to xf86config-4:
1) removed GLCore, DRI (as per readme)
2) changed driver from 'nv' to 'nvidia'

I've messed with the framebuffers (yes/no) and that did nothing. Also adding the Driver option "AGPMode" did not work.

I'm very confused since this worked once but here I am 4 installs later still trying to figure this out. Anyone have an idea?

Okay, if anyone cares here's the answer:

as root type:

modprobe nvidia

This will load the driver. Then, to tell the system to load it all the time, type the following into:

# in /etc/modules.conf
alias char-major-195 nvidia

# in /etc/modules
nvidia

Special thanks to the folks at debianhelp.org for solving this for me.