Your adding cursor pointer to, for example an entire list or the parent UL, instead of the list elements LI.

I have one app that uses a click event on the body of the document and delegates the events depending on what div you clicked. So the entire document now has a pointer cursor.

So be warned if you use Delegation techniques.

Don’t use names for input fields that might’ve been reserved by mootools already – e.g. “send”!
Explanation: Mootools adds a method “send()” to elements (used with Request) – lots of people like to give their <input type=”submit” /> an additional name, so that they can check for a submitted form in php (if (!empty($_POST["send"]))…) – now “send” is already taken by mootools, giving this input another property named “send” would require an overwrite of an element property, which IE (no matter which version) will respond to with an “The Object doesn’t support…” error – should be fixed in MooTools 2.0 but for now, simply avoid names or properties with “reserved” names (e.g. use “sent” instead).
Here’s what I came up with for the “adding link-cursor for clickable elements”-trick (works without errors in any IE so far):

/* update cursor on add/remove click event */
Element.Events.click = {

Element.Events.click = {
base:’click’,
onAdd: function() {
if(this.getStyle && this.get(“tag”) != “a” && !this.match(“input[type=text]“) && !this.match(“input[type=password]“)) {
this.store(‘original-cursor’,this.getStyle(‘cursor’));
this.setStyle(‘cursor’,'pointer’);
}
},
onRemove: function() {
if(this.setStyle && this.get(“tag”) != “a” && !this.match(“input[type=text]“) && !this.match(“input[type=password]“)) {
this.setStyle(‘cursor’,this.retrieve(‘original-cursor’));
}
}

};

It’s still rough (the selector could be refined that makes sure that this style-switching only occurs on elements which aren’t links already or aren’t neither an input-element containing text or an input-element containing a password value (which should show a textinput cursor).

Somehow (don’t ask me why), this.setStyle (which results in setComputedStyle in IE), won’t work in IE correctly when adding Events to Events, “getStyle” however worked…