I have the same problem. My PC has an Intel onboard card and an ATI radeon or even Nvidia card. I could in no way have multiseat on fedora 17 though I had multiseat with the same hardware under fedora 14.
It seems there should be a bug which disables one of the cards when one of which is onboard.
Neither Nvidia proprietary nor kmod-nvidia, nor nouveau, nor xorg-drv-ati and ATI proprietary could not resolve the co-existence of intel with the other cards.
Last edited by masoudjavadieh; 06-20-2012 at 03:15 PM.