The backup/restore job failed because there is already another job scheduled. Delete the timer job from the Timer Job Definitions page, and then restart the backup/restore job.

wss 3.0

admin website perform backup ... why I always get this problem ...

anyway
http://social.technet.microsoft.com/Forums/en-US/sharepointadmin/thread/be9fddf5-b8b5-45f5-abcc-ab1678f8bebc