dbachmann,

When replication is installed *many* of the database security roles that used to work are effectively broken. The reason is that M$ is hardcoding those permissions on the replication stored procedures that are "hooked" at call time when either backup/restore occur. Personally I confronted the same expericence not only at backup time but also at restore time under "certain" conditions. I my opinion Replication stored procedures are incorrectly coded because they are not only called from a wrapper but also from BACKUP/RESTORE.

My solution was simpler in one case that I could afford granting db_owner permissions to that account but in other cases the solution was what you just did. Now if you are in control of the server another trick is to create a pooling job that reads from a table where you post your requests and the job (running under higher privileges ) does the backup for you.

Good Luck