Calling .data({...}) results in a JS exception in jQuery.event.handle whenever a previously bound event handler is fired.

The documentation for .data() says: "Until jQuery 1.4.2, jQuery itself used the .data() method to save information about events that have been bound to the element, using a data item named 'events'."

There is unfortunately still some code in jQuery 1.4.2 that assumes that there is data about event bindings stashed in .data("events"). For example, this line from jQuery.event.handle is the one I'm seeing blow up:

var events = jQuery.data(this, "events"), handlers = events[ event.type ];

A quick search for the JS string "events" turns up two other similar sites: one in liveHandler (non-fatal) and one in jQuery.event.special.live.remove (probably fatal).