Your mouse not working correctly in Marathon on PC is hugely frustrating. Here are some fixes to the known bug you can try. Update: Bungie has released a patch to the Server Slam client that appears ...
The latest news is that Microsoft has published a new support page on this issue, stating that your mouse pointer can ...
Run back through xf86config and try option 4 (PS/2 mouse) or the generic MS mouse options. I find that those two cover just about any PS/2 mouse I've ever thrown at them.