I have exactly the same problem I had everything working fine thenwhilst playing rtcw I had a lock up and now I get garbled screen when starting the dm service. I have no idea how to fix this the nv driver works fine. Arrgghhh!!!
I have a Ti4200 leadtek 128mb ram card.
I also have a Via KV7 mobo (i have noticed that the agpgart module won't load so perhaps it is a flaky NVAGP module problem?