Xserver Problem

[Vineesh <vi...@hc...>]

Hi all,
 I am running a 4 terminal PC with ATI rage LT Pro PCI vga cards & intel
i810 onboard video. 
 Now i want to use SiS 3.3v PCI vga Card. So i purchased 3 of them and
tried. But now there is a big proble. I can start the dispaly on onboard
VGA. I can also start another X server on the second dispaly ie, with
SiS PCI VGA card. But when i try to start yet another one, the whole
system got hanged up. The only way is to reboot. Any one experience same
kind of problem?. Hope u can help me
 regards
   vineesh