Comment 81 for bug 1217585

>rpm -q xorg-x11-drv-nouveau kernel
xorg-x11-drv-nouveau-0.0.16-37.20120306gitf5d1cd2.fc17.x86_64
kernel-3.6.1-1.fc17.x86_64
>lspci | grep VGA
04:00.0 VGA compatible controller: nVidia Corporation GT215 [GeForce GT 240] (rev a2)
>dmesg | grep NV50
[ 1.076393] [drm] nouveau 0000:04:00.0: Detected an NV50 generation card (0x0a3180a2)

Excerpt from /var/log/messages just before system hang (1st 3 lines repeated multiple times over a 1 minute period):
Oct 17 11:27:42 chyna kernel: [349047.152003] [drm] nouveau 0000:04:00.0: PGRAPH TLB flush idle timeout fail: 0x00b00003 0x00000000 0x00005068 0x00000000
Oct 17 11:27:42 chyna kernel: [349047.152003] [drm] nouveau 0000:04:00.0: vm flush timeout: engine 0
Oct 17 11:27:47 chyna kernel: [349051.215383] [drm] nouveau 0000:04:00.0: vm flush timeout: engine 5
Oct 17 11:27:47 chyna kernel: [349056.468056] [drm] nouveau 0000:04:00.0: PFIFO_INTR 0x00200000 - Ch 4

The system is hanging every few days with light usage.
I'll add dmesg output shortly. Let me know if I can provide any more useful information.