If you are running 1.2.3, congratulations on 1) putting up with it until now
and 2) getting a very fine upgrade! :-)  

BEWARE:  You must remove all login logs from the data/stats/player-data
directory.  They have changed in format greatly.  They will cause a crash.  :-)

	cd FICSDIR/data/stats/player_data
	rm */*.logons
        cd ..
        rm logons

Should do it.