Usually it means that the Meridian Mail is down, do you have Meridian Mail or CallPilot, if you have CallPilot whats probably happened is when the upgrade to CallPilot took place they 'forgot' to remove the MMail Configuration.
If you PRT ADAN in LD 22, you'll probably find TTY 8 & 9 still configured for MMail, remove these and the messages will stop.