Comment 10 for bug 1053454

I suffered this once, after upgrading to quantal. At the time, I was having multiple issues - for example, unity performance problems, problems with unity dismissing the "find applications/lenses" overlay, problems booting into gnome-shell.

I was able to submit the report when booting into gnome classic - it's not clear to me if it occurred during that gnome classic session or during the other issues.
My gnome classic session did not display a window manager.

Subsequent reboots, logging directly into gnome classic, have not triggered the problem again.