Issue with window.showModalDialog and overflow:auto in IE7

Question

Here's the issue.

1. I open up a popup using window.showModalDialog in IE7.
2. The popup is a page with a and some filter dropdowns, etc. and a result set at the bottom with is wrapped in a div that uses: overflow:auto.
3. The first time we open up the popup the default resultset dsiplays just fine.
4. But when I click retrieve (to post the form again) I get no results as if no params from the form where passed back to the page.
5. Strange part is that if I don't use window.showModalDialog but simple window.open to open the popup then the above issue doesn't happen and I get the resultset after clicking retrieve.

What's going on here? Can window.showModalDialog supprest passing params from a form within a popup that was opened using that function?

Thanks, goe