The GPO-Admin Snap is struggling to expand the Version Control Root or Notification manager and giving the following error:
End Snap-in. This Snap-in is not responding.
To return to MMC and check the status of the snap-in Click Cancel.
You will lose and unsaved data if you choose to end the snap-in immediately. To end the snap-in click End Now.
When the notification manager is launched it will enumerate the users from our configurations store so that the user can see which users have notifications configured. As part of this it will also retrieve the emails for the users from AD if the user's emails have not been manually entered and saved into the notification manager (this is optional). As this will require an AD call if there are many users set up for notifications and the DC is not close to the GPOAdmin server, this enumeration can take some time. We view this as acceptable as we do not expect users to frequently change notifications in the notification manager. It is meant to be a one-time setup, with occasional edits as necessary.
Normally in this circumstance clicking cancel in the dialogue (it may pop up several times) and waiting will allow the GPOADmin to complete enumeration and act normally. If the user does not click cancel, the MMC will attempt to terminate the GPOADmin console, and it will have to be restarted manually.
Clicking Cancel is the best way to proceed.
If the Notification Manager still does not open after clicking cancel the domain may be slow enumerating the users email addresses. Enhancement ID TF00656893 has been submitted to change the logic in how/when the domain is enumerated. This will be considered for a future release of the product.