Multiseat corrupted screen

[kriko]

I managed to get multiseat working with an gf6600gt and a s3 virge. But I get corrupted screen on geforce 6600gt (blinking pixels):
http://files.myopera.com/kriko/files/multiseat.png

I also got corrupted screen with s3 virge, but I fixed with:
Option "XVideo" "false"
Option "slow_edodram" "true"


If I leave Xorg running for half hour, it will stop doing this on nvidia screen too. What is wrong?

Edit: S3/Virge graphics is on PCI and geforce is on AGP slot.

[kriko]

When on second screen (S3/Virge) I'm making big changes on desktop (like maximizing/restoring windows, dragging...) I hear a squeaking noise out of my speakers. Is it possible that S3 interferes on other components and so making this dots on my gf 6600gt? I don't have any corruption when using just geforce 6600gt (no multiseat).