SCRIPT5: Access is denied in IE9 on file upload

When posting a form with a file upload box using document.forms[0].submit() on ie 9 we get an error that says: SCRIPT5: Access is denied

If I click a few more times it works fine.

As a work around I've caught the error and try a few more times which seems to work just fine.

Is there any explanation on this? The code has worked for years on all the other popular browsers.

The code also works fine in IE9 if the browser is set to IE9 compatibility mode, but that is not something we have general control over.

I've seen references to XMLHTTP being an issue and we do execute a XMLHTTP call but it happens before the button to submit is clicked.