Hey,
I'm running Windows Live Messenger Beta (8.1.0168) and Messenger Live! Plus.
Upon upgrading to the afore mentioned Beta my Custom Event Notifications failed to alert me of anything.
I have completely removed Messenger and ML!P and reinstalled. Still the event notifications do not work. Whether this is a flaw in Messenger, ML!P or my computer setup I do not know. Personally I find Event Notifications the most useful feature of ML!P.
(I have also reverted to the Latest stable Windows Live Messenger to no success.)
/ 
...