Image not clickable below 530px

Hi,

I’m using your great plugin on m wordpress page in my header. The header is 1280 x 520, and I have a small subscribe area that I use with the image map. The image map works great until I resize the browser below ~ 520 px and then the image map no longer works. It just doesn’t seem to be there anymore. At that point, the subscribe image is about 50px x 11px. I was wondering what the issue could be? Maybe the image is too small at that point?

http://wordpress.org/extend/plugins/responsive-image-maps/