This seems to be trigger by the glx module. When I updated to xorg_1:7.2-0ubuntu8, glx stopped working and now the screensaver doesn't mess up gamma correction.
-- screensaver breaks gamma correction of ati fglrx https://launchpad.net/bugs/94019 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
