In my environment, I have SolarWinds Orion monitoring Windows Server 2008 R2 and Server 2012 boxes. Occasionally, monitors will flap or fail, even though the monitored item has not failed or met the failure criteria.
In the event log, I find a service restart and a failure to read the HKLM\SYSTEM\CurrentControlSet\Services\SNMP\Parameters\TrapConfiguration key.
The error in the event log is EventID 1500 in the System Log with an Event Source of SNMP and an error message of "The SNMP Service encountered an error while accessing the registry key SYSTEM\CurrentControlSet\Services\SNMP\Parameters\TrapConfiguration."