I just encountered a DOM implementation issue in IE which took about three hours to solve (and like a year off my life). The story goes like this:
I could not, for the life of me, figure out why a form submitted in Firefox was coming through perfectly while it was missing fields in IE. The form in question has some normal fields and some dynamically generated ones (if JavaScript is enabled). The normal stuff was coming through fine, but I was getting no values for the dynamically generated fields when the form was submitted in IE. I checked the $_REQUEST variable (I am using PHP) to see what was coming through, just to be sure.