I have the same bahvior. Both with nVidia and ATI cards. I do not think it is related to a specific driver. I get this from the gdm login as well as from the login to unlock screen after screen saver.
I have discovered it only happens with passwords longer that 8 characters. trying passwords of 9 and 10 in length, it consistently fails exactly when i hit the 9th character. Passwords of eight characters do not cause the behavior. here are my specs. $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu lucid (development branch) Release: 10.04 Codename: lucid $ uname -a Linux msandman-desktop 2.6.32-14-generic #20-Ubuntu SMP Sat Feb 20 05:18:19 UTC 2010 x86_64 GNU/Linux this is a fresh (today) install and all latest packages updated. ** Also affects: gdm Importance: Undecided Status: New -- Xorg crashes on startup https://bugs.launchpad.net/bugs/527638 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs