Veritas Backup hang w2k server

Hi
My office using win2k sp2, Exchange 2K sp1, Veritas 8.5 with ofo,remote agent and exchange agent.
When I doing a full backup for my server including 2 remote server it will hang when the backup process rich 98% or 99%. No error reported in theevent viewer or log. I need to force shutdown ie using the reset button. By the my server is running Norton AV for exchange and NAV CE. Any expert or whoever experience this before? I can’t get anything from Veritas website.
Thank you in advance.