I’ve been using Ubuntu 9.10 on my Lenovo Thinkpad T60p for a while and decided that I should update my OS to Ubuntu 10.04 to keep up with the kiddies. My setup is having a Dell monitor attached to my Lenovo where I usually do most of my work. After ~2-3 hours of updating packages, I was finally prompted to restart my system. Once the 10.04 desktop came online, I noticed that there were a ton of squiggly rows on my secondary monitor which signalled a bad video output.
I decided to do a quick google search for “Ubuntu 10.04 upgrade squiggly monitor”. This lead me to this forum post: http://www.uluga.ubuntuforums.org/showthread.php?t=1466072
Several forum posters reiterated what the OP was mentioning and finally, someone had a solution:
“create file /etc/modprobe.d/radeon.conf with contents “options radeon new_pll=0 modeset=0″ and reboot.”
Boom, I did that and all is good now. If you want to follow this bug, here is a link: https://bugs.launchpad.net/ubuntu/lucid/+source/linux/+bug/541501