This should not be happening anymore unless one of your Administrators is physically resetting the Who's Online recordbook inside the Control Panel. Didn't I install your WOL personally?
Are you using UBB on a Win95/Win98 machine by any chance?
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.