I have the same problem.
Just updated to xorg-server-1.4.99.906 and xf86-video-ati-6.9.0 but Xserver still freezes without usb-mouse plugged in. I'm using kernel-2.6.26.3 with ArchLinux patches.
Booting the kernel with nohz=off or disabling DRI in xorg.conf solve it for me.
I have the same problem.
Just updated to xorg-server- 1.4.99. 906 and xf86-video- ati-6.9. 0 but Xserver still freezes without usb-mouse plugged in. I'm using kernel-2.6.26.3 with ArchLinux patches.
Booting the kernel with nohz=off or disabling DRI in xorg.conf solve it for me.