I solved the problem for myself by deleting the file which is producing these stupid notes with
sudo rm '/usr/lib/tomboy/Plugins/NoteOfTheDay.dll'
and
killall tomboy
After restarting tomboy, everything works out again. The "Notes of the Minute" are not there anymore, but everything still works. I don't know if this is a good / the correct solution, though, but it works for me.
I solved the problem for myself by deleting the file which is producing these stupid notes with
sudo rm '/usr/lib/ tomboy/ Plugins/ NoteOfTheDay. dll'
and
killall tomboy
After restarting tomboy, everything works out again. The "Notes of the Minute" are not there anymore, but everything still works. I don't know if this is a good / the correct solution, though, but it works for me.