One of my SME5.6 servers becomes unstable at approx 51 days.  The server-manager screen shows, but doesn't accept keyboard strokes.  The network is unresponsive.  The only solution is to power down the server.  Twice now I've had printing problems after a lockup and had to delete /var/cache/samba/ntprinters.tdb and /var/cache/samba/printing.tdb
Then I shutdown lpd, restarted smb and started lpd.
I am then able to print.
I did a search on this file and found others with the same issue.