Open services MMC, stop the agent service, open the properties, enter "-debug" as a startup parameter and start it again.
That should create files in the Logs folder within the Backup Exec installation. You can do it with the job engine service too. Just remember to clear that parameter and restart the service once you've figured it out because the logs can get quite big!
I've had my fair share of problems with BackupExec, but your setup sounds pretty straight forward!
It's worth turning off AOFO if its on as it can take a long time to do the snapshots and cause jobs to time out (although the error would be more specific if this was the problem). Try taking the system state out of the selection list too temporarily