I have a solution to a problem I hadn't asked, but it might help someone else with the same problem.

Running
Debian Lenny/Sid (aka testing/unstable)
kernel: 2.6.24 (custom-compiled for K7 architecture)
on a 64-bit (dual-core) AMD Athlon
Nvidia GeForce 6150LE graphics card
using the proprietary Nvidia driver.

After a recent upgrade (I update/upgrade daily) none of my linux graphics-heavy games would run (Sauerbraten, Nexuiz, Alien Arena, Warzone 2100, Warsow)
Executing said games from the command line gave me varying error messages concerning GLX, Mesa, SDL, whatever.

Well, my best guess was that at least one of the xserver-xorg modules was upgraded, which caused some sort of problem/conflict with the proprietary Nvidia driver.

What I did:

using the proprietary nvidia driver, uninstall the driver and reinstall the driver. If you're already using the proprietary driver, then you already know how to do this.

DISCLAIMER: I could be dead wrong as to the explanation of why this worked... I'm not a linux expert, I'm just good at "winging it...."

Hi,

Uh, no offence, but are you sure athlon64 is K7? I've always put them under K8...

Serafean

You're right, it is K8, running one myself.