Re: GPU at $BUSID$ has fallen of the bus
Apart fron the "NVRM: GPU at 0000:04:00.0 has fallen off the bus." message, I have the exact same symptoms as luudee.
In my case, ususally is mplayer (both windowed and fullscreen) that triggers the freeze.
I'm running a full up-to-date Arch Linux, x86_64, with latest official nvidia drivers, GT240.