The game loads up fine... I can work with all the menus and whatnot in the pre-game screens, but when I try to actually connect to a server, it'll connect, download a map/skin/texture if I need it, then start to load the game- at which point it inevitably crashes and burns- dumping me back into X with a screen at an ultra-low resolution, and with my mouse still captured.

This is very annoying...

I'm running slackware 9.1 : Nvidia GForce 2 card, with the latest Nvidia drivers installed :
CPU PIII 700 : 240M of RAM : Gnome Session with FVWM for a window manager :

Hmmm.. You've gotten longer than i have...

To me it works great until i get the serverlist... First i didn't get any servers listed at all. and a bit of tweaking and updating have now gotten me to the point where i get some servers listed, all of them with a ping of 1.
So either is something gone wrong woth my tweaking too, or i've managed to upgrade my connection.

Does your screen fill up more than the monitor? in so case try "ctrl"+"alt"+ "numpad+" or "numpad-" to change screen resolution.
It works for me most of the time