on line 1919 in the uncompressed jquery-1.4.2.js:

I get a bug where events == undefined in IE7 (7.0.5730.13)

the same bug is present in the minified file jquery-1.4.2.min.js

a fix could be to change

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

into

var events = jQuery.data(this, "events");

var handlers = null;

if (events) {

handlers = events[event.type];

}