Have you seen this: SolarWinds WMI Troubleshooting Guide?
I would first have a look at that. Typically though, if you are being rejected because you don't have rights or some permission related issue, you will find a DCOM error in the Windows events, but you said you aren't seeing that.?.
Are you running a firewall or AV software that could be blocking the ports that WMI/DCOM communicates on? Try shutting those off.
Are the Orion server and the server being monitored in the same domain, outside a domain, etc?
Also, I will tell you that we ran into a very similar issue recently with a 2008 SBS server. The server was a DC and one of the applied patches had disabled the Remote Registry Service, we believe. We also had problems when we moved the server out of the domain. The local certificate store was possibly modified during the domain add/remove but when we recreated the credentials and the service was started again, everything worked fine after that.
Hopefully, that will give some options to look at to get you to resolution.
... sorry, i made reference to an Orion server but you are running ipMonitor. The same application should apply though. ;-)
thanks for the replies.
I did, however, sort the issue. It appears that even though the account i was using was in the administrators group I had to explicitly give the use account full access to WMI.
No sure why but it worked.