Have your WMI monitors been reporting down services when in fact your services are up? You may need to increase the default length of the RPCPingTimeout registry value so that you are given a longer chance to connect.
To edit the RPCPingTimout registry value:
HKEY_LOCAL_MACHINE\SOFTWARE\Ipswitch\Network Monitor\WhatsUp Engine\2007\Settings
Important: The default timeout is 5 seconds. We strongly recommend that you do not exceed a timeout of 30 seconds.
After making any changes to the registry, you need to restart the WhatsUp Engine.
To restart the WhatsUp Engine: