The attached patch (which I adapted from a fix for 2.4 kernels that I found -- sorry I've lost the original reference now) fixes the corruption.
P.S. Why can't I attach a file to the original report? -- Corrupted output on external monitor/projector for iBook https://launchpad.net/bugs/53882 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
