Let me have 1 more go at the thwack discussion with the most responses! Let's do this 1 step at a time.
Remote desktop to the SolarWinds server, browse to the installation folder - typically Program Files (x86)\SolarWinds\Orion and you should find a utility called snmpwalk.exe. Launch that, punch in the OID that is giving you all the heartache, put in the IP and SNMP community string of your riverbed device you have been testing against, and click on the Scan button. Post the contents of the scan results.