Backing up workstations and jobs are being suspended

Have an older NB environment and backing up workstations.  The jobs run, but over time, get suspended after about 10 hours.  Need help finding out why and how to solve this.

Master server is only server and backing up to DataDomain appliance using OST.

Again, backing up workstations and the speeds are horrible and the backups do run for many hours if not days.  I suspect it could be a timeout setting, but need help diagnosing it.

Thanks in advance!