Installed Ubuntu Oneiric Ocelot 11.1 a few weeks ago without issue on my AMD dual-core desktop machine (home-built) with AMD/ATI Radeon XFX "HD 4350" graphics card. Recently I was trying to update GRUB 2 to detect my Windows 7 installation on the machine, and followed instructions on this page -- which resulted in GRUB failing to load upon restart (I got the "grub rescue" prompt).

In trying to recover from my new problem, I followed some instructions on this page -- mainly this bit:

sudo -i

mount /dev/sda7 /mnt

mount /dev/sda6 /mnt/boot  #skip this one if not have a separate /boot partition

grub-install --root-directory=/mnt/ /dev/sda

which has now resulted in my main problem:

MAIN PROBLEM:

Now my computer will boot to GRUB, but if I let it load Oneiric the screen will go blank immediately afterward and stay blank after reboot -- also, the monitor will turn off and claim "no signal". This can only be remedied if I boot to the LiveCD and then turn my monitor off and on again*.

My extremely ignorant opinion is that this is some kind of graphics card detection problem, but I don't know how I caused it or how to fix it. Thoughts?

I have also recently been trying to troubleshoot (i.e. googleshoot) some problems related to graphics in Gnome 3 -- I don't have specifics unfortunately, and no step I took resulted in bad behavior immediately afterward, but I suppose I might have screwed something up.

*At first I thought the recovery process was more complex but have since simplified it.