Just upgraded to Live Messenger 2011 and Plus! 5
In previous versions minimizing live messenger to the notification area (by selecting close ( X ) ) would minimize both messenger and the event viewer window. Likewise restoring messenger, restored both messenger and event viewer - they were tied together!
In the new version - action on the messenger window does not affect the event viewer window - they are no longer tied.
This means that the event viewer window cannot be minimized, only closed (or full-screen). Doing this means you have to re-enable the event viewer window every time you resore the messenger main window!
NB. When using multiple messenger instances - the event viewer window, for the active messenger window, is brought to the front!