OK, could you please do the following?
First start tomboy from a terminal. Does this crash too? If it crashes please paste the output here.
Otherwise start tomboy as "tomboy --panel-applet" in a terminal, leave this running and while it's still running add tomboy to your panel again. It should crash now again with more useful output on the terminal. Please paste this here.
If this doesn't crash but normal adding to the panel still crashes please look into your ~/.xsession-errors if there's some output from tomboy and paste this here.
OK, could you please do the following?
First start tomboy from a terminal. Does this crash too? If it crashes please paste the output here.
Otherwise start tomboy as "tomboy --panel-applet" in a terminal, leave this running and while it's still running add tomboy to your panel again. It should crash now again with more useful output on the terminal. Please paste this here.
If this doesn't crash but normal adding to the panel still crashes please look into your ~/.xsession-errors if there's some output from tomboy and paste this here.