Comment 2 for bug 272086

Those warnings are innocuous and not the cause of the bug, but I'll get rid of them anyway. discover is no longer used in ubuntu.

As to the problem, it looks like you have a mismatch between your xserver, mesa, and/or driver version, but without more info it's hard to say. See http://wiki.ubuntu.com/X/Reporting for tips on how to correctly report X bugs.