Not sure if it helps in this particular problem, but you might try to edit your xorg.conf and comment out / remove the line that says 'Load "dri"'. Then you don't have accelerated 3D, but it'd be worth trying out if it helps in this.
This might be a duplicate of bug 6111, but there's a lot of noise (unrelated to the original reporter's problem) there. A hint from there, which is probably unrelated to you since you already have a PCI card, is to add Option "BusType" "PCI" to the Driver-section.
Not sure if it helps in this particular problem, but you might try to edit your xorg.conf and comment out / remove the line that says 'Load "dri"'. Then you don't have accelerated 3D, but it'd be worth trying out if it helps in this.
This might be a duplicate of bug 6111, but there's a lot of noise (unrelated to the original reporter's problem) there. A hint from there, which is probably unrelated to you since you already have a PCI card, is to add Option "BusType" "PCI" to the Driver-section.