Re: GT430 + 260.19.21 + VDPAU = artifacts
For what it's worth, I experience the same artefacts running mythtv on GTX260 (ubuntu 10.10 with driver 260.19.21). In my case the problem appear after a crash in mythfrontend (running bleeding edge code so I'll have to live with a few crashes) which the X-server doesn't seem to be able to recover from. When the player is restarted black (or very dark) pixels are distorted. The X-server must be restarted to restore proper video playback through vdpau.
correction: it's not always enough to restart the x-server, it may also be necessary to re-load the nvidia kernel-module