Hi Chris.
I just looked at the source code for the buttons in your order page and noticed that there’s something wrong with some of the hidden input fields for the buy-now button. I think that’s what’s preventing it from working.
It’s probably being done by something that the theme or another plugin changes in the filtering of the page’s content.
Could you do some quick tests? First change for a moment the theme to the default TwentyEleven and reload the order page to try the button again. If the problem continues, test the other plugins, deactivating them one by one, checking after each if the problem continues.
If you can replace the plugin/theme for one without the problem, that’s good. Otherwise, you can try fixing it, or telling the developer about it so he can fix it.
If neither one is an option, you could try removing the content filters one by one (except do_shortcode) trying to fix it. http://wordpress.org/extend/plugins/trueedit/
Another thing you can try is enabling button encryption. It it’ll output a different code for the button, which may not be affected adversely by the content filtering. [hilite path]Dashboard -› s2Member® -› PayPal® Options -› Account Details -› Encryption[/hilite]
Yet another thing to try, is editing the button’s template, removing all line-breaks and HTML comments, but you’d need to edit this file again after each update. s2member/includes/templates/buttons/
I hope that helps! :)