Sorry for the inconvenience. DriveHQ Online Backup 4.0 added a new feature by default - the software now runs in service mode. So even if nobody is logged on, the backup process can still run. Now this introduced new issues with network backup. Please visit this page for more details:
http://www.drivehq.com/help/doc/backup_help/serviceandnetworkbackup.htm
Basically, you just need to change the "Windows service logon user" of Online Backup service.