ARCserve not backing up Oracle.

We have a Windows NT 4 Server SP6 with , Oracle 8i Release 8.1.5
We are running ARCserve 2000 Adv Edition build 1100 and Oracle Adv/Work Group Backup Agent for Oracle Server.
I am unable to backup the Oracle database. I receive the error

Error8601 Failed to connect agent. (AGENT=dbaora7@ORCL, EC=Backup Agent Error –(85)”Invalid user ID or password was submmitted.”.)

Following CA’s technical support I have confirmed that the SID is correct. We are using the “internal” user name and password in the security settings for the backup job.
We have confirmed that the internal username/password is correct from a command prompt. We receive this message when trying to back up other databases on the network also.

Any help would be much appreciated.