I tried installing ubunutu on my macbook pro (7,1 I believe, with lion 7.2 installed) today and ended with result of a nonbooting computer, the ubuntu partition won't boot either! I'll try to explain all the steps.
1. I first installed rEFit.
2. Next I booted from a burned copy of the latest release of ubuntu on a dvd.
3. I created a partition of 5120 mb from the freespace on my harddrive, I made sure to leave the mac partition intact.
4. I finished the install, it said to ejct disc and hit enter, I did, the computer froze. I ended up having to hold the power button.
5. The computer just showed a white screen. It wouldn't boot to the rEFit screen or anything. It just resulted in falling back to lions recovery partion. Disc utility couln't verify ubuntu's or lion's partitions.
I am at a loss. Please help