Here's what I've encountered regarding event structures and panel-locking (LV 6.1 and 7.0):
(1) If you check Lock Front Panel for an event, that doesn't truly lock the front panel. As other people have noted, other events can be generated from front-panel controls while your event is running. They're queued while the panel is locked, then fire as soon as the panel is unlocked (i.e. when the event case is finished running).
(2) You have to be careful using the disable-button-via-property-node strategy:
