Description of Problem: gnome panel crashes. traceback attached
Created attachment 88204 [details] traceback
This one is tracked on gnome.org, may be fixed in newer panel versions, need to link to the gnome.org bug from here.
Are you using a transparent panel? http://bugzilla.gnome.org/show_bug.cgi?id=97487
Have you seen this again? Were you using a transparent panel? I haven't seen other reports, so I'm guessing fixed.
Not seen it recently ... close it.
Closing per reporter comment