I am having a similar problem, but none of the posted suggestions seem to apply. Here's the scoop. I have set up two maintenance plans for a database. One does just the log backups and the other does everything else, including data backups. Together, these created several SQL jobs. All jobs run fine (including the log backup) except for the data backup - so it doesn't appear to be a problem with xp_sqlmaint. If I copy the data backup task and paste it to Query Analyzer, it runs fine - so it doesn't appear to be space problems or any problems associated with any of the switches in the command line.

Any ideas?