Help... I'm not sure what causes this or how to debug it...

On my base page I have an <iframe> embedded in a <div> that displays another URL.

I have another <div> on the page where I set the style 'display' from 'none' to inline to pop open a little dynamic 'window' that contains a form with some input fields.

The fields in the popup window form partially overlap the iframe div (but after submitting the form, the popup window goes away and you can see the iframe).

When you click on one of the form text input fields you can see the text cursor and you can see the cursor as you move across the field while you type. But as soon as the cursor is in the part of the field that overlaps with where the iframe is (which is behind the popup), the text cursor doesn't draw. I can still type though and the new characters draw in the field...

Why does the text cursor/caret disappear when the field overlaps the iframe? How can I fix this? Other than the text cursor not being visible, the rest of the form and field look and work OK.