TYPO3 Core

I can confirm this behaviour

The problem is that some JS in IE call the functions
pointerX: function(event) { return Event.pointer(event).x },
pointerY: function(event) { return Event.pointer(event).y },

(line 3796 in typo3/contrib/prototype/prototype.js)

with a not valid event, which causes the
pointer: function(event) {
return {
x: event.pageX || (event.clientX +
(document.documentElement.scrollLeft || document.body.scrollLeft)),
y: event.pageY || (event.clientY +
(document.documentElement.scrollTop || document.body.scrollTop))
};
},
(located right on top of the above functions)
to throw an error.

A workaround is to ad if(event) around things using Event.pointerX and Event.pointerY .

The result would be:
mouseMoveEvent: function(event) {
if (!event) {
event = window.event;
}
if(event){
$('dragIcon').style.left = (Event.pointerX(event) + 5) + 'px';
$('dragIcon').style.top = (Event.pointerY(event) - 5) + 'px';
$('dragIcon').style.visibility = 'visible';
}
return false;
},
in typo3/js/tree.js
calcMousePosEvent: function(event) {
if (!event) {
event = window.event;
}
if(event){
this.mousePos.X = Event.pointerX(event);
this.mousePos.Y = Event.pointerY(event);
this.mouseOutFromMenu('contentMenu0');
this.mouseOutFromMenu('contentMenu1');
}
},
in typo3/js/clickmenu.js
draw: function(event) {
if(event){
var pointer = [Event.pointerX(event), Event.pointerY(event)];
var offsets = Position.cumulativeOffset(this.track);
pointer⁰ -= this.offsetX + offsets⁰;
pointer¹ -= this.offsetY + offsets¹;
this.event = event;
this.setValue(this.translateToValue( this.isVertical() ? pointer¹ : pointer⁰ ));
if (this.initialized && this.options.onSlide)
this.options.onSlide(this.values.length>1 ? this.values : this.value, this);
}
},
in typo3/contrib/scriptaculous/slider.js

I'm sure that there must be a better solution e.g. finding out why something is called without the proper event - but it has not been possible for me to locate it.

The code above has removed the problem from my IE7, but there could be other places where it gives ploblems

Using window.event for IE7 is somehow related to #26618.