Re: GeForce 7600 GS blank screen on reboot
No, the kernel module is not unloaded because the screens don't have a usable configuration, its the other way around.
You shouldn't need to specify an IOMMU just to start X. If you do, that's a BIOS bug.
At this point, there isn't any clear information in your bug report to indicate why X is failing. If you could setup a serial console that might capture any kernel messages that were generated when the system hangs.