Which snapins does MMC.exe have loaded? Do you have Server Manager loaded and have you looked at other snapins such as IIS since opening Server Manager?
I would recommend one of the following:
1) Disable the automatic refresh of Server Manager. At the bottom of the main Server Manager page, you should see a link to configure the refresh. By default the refresh runs every two minutes and can certainly cause page faults over time.
2) Close Server Manager when you are done using the UI.