[Steven Zahm]

@ simon

Yes, this is theme conflict. It seems to be using a fairly old jQuery script to enhance select drop downs.

Does the theme perhaps have an option to disable the way it enhances select drop downs? If it does not, then the only option will be to edit this file. I think removing this line should remove that feature without any negative effects.
jQuery("select").selectbox();

Hope that helps! Let me know.