How far back would you suggest? I have 12.04 installed right now and freezes right after booting to the desktop.
Honestly, today, I'd try 14.04, it was just released and pretty slick in general. You may actually find a newer version will fix something that existed in 12.04. I'd try this first.
Failing that, you may want to try Debian Wheezy, it's not unsimilar to a 'core' version of what is in the *buntus.
~S