Exact the same issue here with an iiyama E1900ws. 915resolution and editting xorg.conf solves the problem, allthough it is rather anoying.
-- X.org doesn't detect widescreen resolution https://launchpad.net/bugs/63551 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
