Computer all of a sudden getting owned framerate-wise

[Led]

I have:

AMD XP2800+.
1.5 gigs of ddr ram.
GeForce 4 ti4600.

Suddenly my framerate is going through the hole. It is becoming nigh impossible to hit anything, because everything stutters horribly

Is this a bug introduced in a patch, or is it something more sinister on my end? I have not installed anything new recently, just the performance has slowly degraded over the past few weeks...