I am having a backup problem and need some advise, pls?

ArcServe 11.1 SP3 on NW65SP8 cancels backup as soon as its started.

Backup Server: NetWare6.5 SP8
Backup Software: ArcServe 11.1 SP3
Tape Device: HP Tape Library Ultrium3 x 8
Server Hardware: HP ProLiant ML350G3 - will be upgraded at the end of this year
Agents on: NetWare6.5 SP8, Windows2003SP2 and R2SP2, SLES10SP3 + OES2

The backup job had been working okay until two weeks ago, but backup has never get success due to errors, and I found that as soon as backup starts, it fails.

Activity Logs shows:
Backup Canceled - User Initiated

Job Log shows:
"Missed from Backup"

Above errors happens on all servers regardless NOS since two weeks ago.
It does happen even on the data on local server.

We have not done any changed on any servers at all.

CA states they do not support AecServe11.3 on NW65SP8 that's funny, so CA does not support this problem, unfortunately.

I did run manual backup to backup tiny files on the local server, it works fine.
I have not tested big data backup yet.

Please, give us some advise, pls?