See this post:
http://forum.ppcgeeks.com/showpost.php?p=1406183
Disable Notifications
Get a registry editor, and find the key HKLM\Services\NOTIFICATIONMANAGER\Flags. It should be 0 by default - change it to 4. This stops the HTC notification manager running and restores the default WM functionality.
Check the value of the key. If it is not 0, then change it back to 0.