Oh...yeah, I didn't notice that your code includes a form, and I think the problem is that for admins and moderators the posts are already inside a form, and you can't nest them.
Given that there's only one input field (SearchBy) and it's method="GET", it should be the same as going to the url
http://www.pollstar.com/eventSearch....archBy=keyword, so you could probably replace the form with some javascript that sets location.href to that url. But you'd also need to encode the search term for a url...it starts going from an easy hack to a complicated one.