I have a strange error with searching in IE8 and zip code. It may not be a search in the zip code per se that calls it - just an AJAX call that changes the selection. I created a test page here . If you click "Find Address" and then double-click (fairly quickly) on one of the addresses that are within the border with a red edge, you will see an error below in IE8.
Note. I found that it is incompatible with reproducing the error, but if you scroll the list of addresses right to the bottom, and then double-click on the go to Holly Cottage, it should reproduce the error.

If someone can shed light on this bizarre behavior, it will be very grateful. Is this an IE8 bug?