One of the more common issues that I run into is WMI communications problems. WMI (Windows Management Instrumentation) is an SNMP like framework that exposes a ton of Windows system information. The good news is that it is part of a standard install with Win2k, WinXP, Win2k3, WinVista, and Win2k8. The bad news is, oddly enough, it only works with Windows systems.
If you are having WMI connectivity issues with WUG, first check the obvious stuff;
1. Username and Password are correct.
2. Username has administrative privilege on the system you want to monitor.
3. The IP/Hostname is/are correct.
If you have checked all of that, look at the event log on the monitored system. See lots of Kerberos errors as you have been attempting to chat with the device? If yes, check the time on the monitored server and the monitoring server.
If you remove all time zone differences (figure back to UTC 0, or GMT) what is the difference? If it is more than 3-5 minutes, WMI monitoring will never work. The security ticket is expired before it’s ever used, or worse is issued for a time that hasn’t occurred yet.

In this case a simple time change may fix the problem. Now this is a temporary fix, as the Mickey Mouse watch I had in second grade kept truer time than most PC’s. You will want to look at setting up a time server to keep this from happening again. And while you are at it, set up a NTP monitor for that new time server.