I have a nVidia Quadro FX 570 dial dvi video card. When I configure xorg with 1 serverlayour with 2 screens in it, the computer works as expected. But, when I make 2 serverlayours (for multiseat), the xserver fails to start. It suddenly it stops at the first layout and says that the device (videocard) does not exist.

Does anyone know why this would be happening?

Thanks,
-Adam

I may be wrong but I do not think that this card supports a true multiseat setup as both monitors share the same frame buffer. That is the first thing I would check out.

I've tried the same for a while. I didn't have that particular card, but it was another nvidia card. After googling around I found out that there is a bug or some complications with multiseat and one graphics card.

I personally didn't settle for this, so I spent a lot of time configuring multiseat with one card. I didn't manage to get this working with kdm or gdm. xdm on the other hand at least manage to activate both screens with keyboard and mouse working separately. It was also possible to log on on both xservers.

It was even possible to use both of the screens independent of each other. But as soon as I loged of on of the accounts the problems started. I don't remember what happend, but it didn't work. Either both of them got loged out, or the xservers froze. I don't quite remember.

One thing I didn't try, and I don't know if it even will be possible. I tought of it right now. But it could perhaps work to set up kdm on xserver :0 and gdm on xserver :1. Good luck. Write a howto if you get it working