there gnome-session really terminates and all evidence is gone.
to find any traces in log files.
timestamp of 0.  This shouldn't happen!
"... this program is likely to crash, leak or unexpectedly abort soon..."
(see bug 241959) so maybe those are more than just a noise?
stuff too for sessions which terminated apparently in a normal way.
After a crash /usr/libexec/wnck-applet does not go away after 'kill'.
I do not recall seeing such crash for a while.