Here’s one that might stump you occasionally. You open the Admin Console and instead of popping open you have to wait a few minutes before it opens. Once open all is fine. What happened?! It may have been looking for the SCOM server. If VMM and SCOM are integrated and the SCOM server is down, this can happen. Has this happened to you before? Check the Application event log on the VMM server for the event below. If you see it, this scenario was probably the case. The workaround is to have the SCOM server up when you open the VMM Admin Console.
Log Name: Application
Date: 2/15/2013 12:21:49 PM
Event ID: 25935
Task Category: None
AllChildHosts property is null. Can't compute capacity, so monitor wouldn't work