I had an issue this past weekend when I noticed I didn't have current statistics for any of my interfaces. After checking various items, I found the following error in Event Viewer:
Faulting application NetPerfMonService.EXE, version 7.6.0.1, faulting module SNMPv7.dll, version 7.1.0.21, fault address 0x0000bbd5.
Rebooting the Orion server resolved the issue. One week ago I upgraded from 9.0 SP1 to SP2. During the upgrade I had problems getting the NetPerfMonService to stop; after waiting 3 hours as the memory crept downward every minute by 128 k, I killed the processes, allowing the upgrade to complete, but then had to reboot when it wouldn't restart automatically at the end.