I remember to have been able to reach the NS_ABORT in debug mode. That does not seem to be what you want. Shouldn't we rather pass the event to another handler?
The NS_ABORT was added in http://hg.mozilla.org/mozilla-central/rev/a41df1f97f0d Listeners are added for "mouseover", "click", and "mouseout". The code seems to expect that "click" changes to "mouseclick", but that might be a mistake.
Yes, that's just a typo, the "mouseclick" should be changed to "click"
In my queue :-)
(Clearing to stop this request showing up on the 'My Requests' page)