WMI authentication issue

Hi there all, and my complimets to OpManager authors, very nice software.

I'm testing OpManager as monitoring software for my company.
I'm having a problem on a couple of servers with WMI credentials; when I test credentials on these two machines I have SNMP Passed and WMI Failed so I'won't be able to monitor windows services.
Am I missing to configure something on remote machine?
I've also tried to authenticate with local admin pw instead of the domain user but still no way.

Thanks for your help

DM