Nope, it's not a recent regression. It's being happening since oneiric at least, or that's when I noticed it. I have not tried with anything newer than the latest development raring that I use currently. I think that it makes sense to contact X.org next and link them to this bug report
** Changed in: xserver-xorg-video-ati (Ubuntu) Status: Incomplete => New -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-ati in Ubuntu. https://bugs.launchpad.net/bugs/1085338 Title: One pixel column that belongs in one monitor shows up in the other instead To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/1085338/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp