[Bug 76902] Switch user crashes system.

[Malius]

Public bug reported:

Binary package hint: gdm

When I attempt to switch users, the system hard locks (i.e. The only way
to free the system was to hit the reset button).

Specs of possible interest:
1.  Ubuntu Dapper with all the latest patches (Upgraded from Breezy).
2.  ATI Radeon 9800 pro with official drivers.
3.  Athlon 1800 processor.

Steps leading to the issue:
1.  I log into my default account (The one I created during installation).
2.  Once the desktop is available, I Select: "Quit...", "Lock Screen".
3.  I have the "Blank Screen" screensaver active, so I move my mouse to get the password dialog.
4.  I select the "Switch User" button.
5.  I select the user account I wish to activate.
6.  The screen switches to tty 8 and then the system locks.

Note 1:
I've tried the following in response to the system locking:
1.  Ctrl-Alt-Backspace
2.  Ctrl-Alt-Delete
3.  Ctrl-Alt-Fn(N) - Where 'N' is all of the function keys.
None of the above produced any results.  In fact the keyboard indicator lights have all been disabled at this point.

Note 2:
I can reproduce the locking sequence by typing:
gdmflexiserver -s

Note 3:
If I attempt to switch users without locking the screen, I am successful roughly 1/3 of the time (i.e. sometimes the system locks, and other it works as desired).

Note 4:
Typing: "gdmflexiserver --debug --xnest" produces no errors and brings up a nested login.

** Affects: gdm (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed

-- 
Switch user crashes system.
https://launchpad.net/bugs/76902