Is it normal for nbostpxy.exe to exhibit 99% CPU utilisation whilst a backup is running, the box in question is running 2008 R2 SP1 8Gb RAM with SQL 2008 R2.
The high CPU utilisation occurs during each hourly incremental SQL backup and continues for a couple of minutes after the parent jobs is marked as sucessfull in the activity monitor on the master server?
The process is involved with deduplication processing on the client. If you're running client side deduplication it might be a good idea to change it to media server deduplication.
Is the system x64 (it should be)?
here is some basic requirements to run dedupe engine:
http://www.symantec.com/docs/HOWTO70489 take note of the proportion of RAM & CPU to storage.