One of the requirements of the dialog is that it appear as the top-most element. The only way to accomplish this consistently in Internet Explorer is to have the dialog be the last element in the body, as it respects DOM order over z-index. There are generally two work-arounds:
1. move the dialog element back somewhere else in the dom in the open event callback. This has the potential to allow other elements to appear on top of the dialog (see above)
2. move the dialog content element somewhere else in the dom in the close event callback, before the submit.
Neither of these are suitable for building in to the dialog, and are left as suggested work-arounds. As the first comment on this ticket suggests, this needs to be documented better.