Where to start.... My OS is Ubuntu Server 12.04.2 AMD64 (no specific reason to get server other than avoiding any preset desktop environment right out of the box).
I was having the fun of my lifetime with my switch from Windows to Ubuntu thanks to a NAS issue, scanner not working etc etc when I swapped graphics card with a friend (switched from GTX560ti to GTX 550ti. This is temporary) and the OS stopped booting. The graphics driver is nouveau and the boot usually stops after detecting keyboard so I suspected that driver. I chrooted into the system, but couldn't find any way to reinstall, reconfigure or even remove old config of nouveau. I could not find any standard way to debug boot issues other than a suggested ssh hack that . Before I was able to attempt that, the system somehow became even more damaged and now boot stops right at grub. I can see no grub menu, nothing. Repairing grub did not help.
If nothing else works, I am switching over to 12.10 Desktop and purging gnome post-install because that OS has got a repair install option if I heard right?
Update: I have fixed grub, but Ubuntu is still getting stuck during boot.