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When you drag the map and release the mouse click outside the map div, _downLock variable remains at true in interaction object. (Tested on google maps/leaflet/modest maps on http://mapbox.com/wax/)
The ideal would be to use an event like 'mouseleave' to trigger the off function of interaction. But I didn't see this event in bean.js (or I missed it).
mouseenter/mouseleave are proprietary IE events (with partial reimplementations in jQuery). Might be able to work around this situation by binding clicks to the document rather than the map.