Feedburner Email Submit triggers Search Query

I just came across a weird situation when adding the email form for Feedburner.

If I copy and paste the code into the sidebar, whenever I type in an email address and “Subscribe”, WordPress will instead run a search query for that search term.

After much trial and error, I discovered that the only way to get the form to work is by having two copies of the submission form. The first copy I can clear out while keeping the <form action==”…”></form>. Then the second instance of the code has the complete code.

For example:
<form action="https://feedburner.google.com/fb/a/mailverify" method="post" target="popupwindow" onsubmit="window.open('https://feedburner.google.com/fb/a/mailverify?uri=<?php echo $wp_mediamag_fb_feed_id; ?>', 'popupwindow', 'scrollbars=yes,width=550,height=520');return true"></form><li class="email"><form action="https://feedburner.google.com/fb/a/mailverify" method="post" target="popupwindow" onsubmit="window.open('https://feedburner.google.com/fb/a/mailverify?uri=<?php echo $wp_mediamag_fb_feed_id; ?>', 'popupwindow', 'scrollbars=yes,width=550,height=520');return true"><span>Subscribe via email:</span><input type="text" id="sub" name="email"/><input type="hidden" value="<?php echo $wp_mediamag_fb_feed_id; ?>" name="uri"/><input type="hidden" name="loc" value="en_US"/><input id="subbutton" type="submit" value="Subscribe" /></form></li>

I know this isn’t the best way to fix things but haven’t been able to figure out the cause. If anyone has a suggestion, it would be much appreciated.