Feedburner form html issue

Hi All!

I’m sorry to ask about something like this; but it’s very late and I’ve been working for the last 48h.
Quite recently I’ve set up a new website, which uses feedburner for subscription.
The basic form came in with the template only needed adjusting to the account etc.
Once I’ve done it, I’ve noticed a problem; once I submit the form I get the feedburner confirmation window as a pop-up and the same starts to open in the main window.
Pure madness. I only want the pop-up window, so I’ve been trying to adjust the script, and I’m stuck as the feedburner confirmation loads always in the main window.
For now I’m stuck with this:
<input type="hidden" value="https://feedburner.google.com/fb/a/mailverify?uri=WoRecordsManagement" onsubmit="window.open('https://feedburner.google.com/fb/a/mailverify?uri=WoRecordsManagement', 'scrollbars=yes,width=550,height=520')">

And there is no pop up at all right now, it only loads in the main window.

For reference, here is the whole bit of the form code:

<form action="https://feedburner.google.com/fb/a/mailverify?uri=WoRecordsManagement" method="post" class="subscribe">
	<fieldset>
	<input type="text" class="feedinput" value="Your email address ..." name="email" />
	<input type="submit" class="feedsubmit" value="Join" />
	<input type="hidden" value="https://feedburner.google.com/fb/a/mailverify?uri=WoRecordsManagement" onsubmit="window.open('https://feedburner.google.com/fb/a/mailverify?uri=WoRecordsManagement', 'scrollbars=yes,width=550,height=520')">
	<input type="hidden" value="<?php echo $blog_title; ?>" name="title"/>
	<input type="hidden" name="loc" value="<?php echo $location; ?>"/>
	</fieldset>
	</form>

Summarising, I want the form submission to only open a pop up that will display the feedburner page, and the main window to stay the same.

Please help me out here, as I feel so stupid right now… ??