Code for buttons displaying

Hi! For the last couple of weeks, I have been receiving notifications from people that my buy buttons are replaced with the original code. This is on my site speakfromday1.com, and for several browsers. It’s not consistent and users report different browsers and systems from which the problem is seen. I myself see the code fine. Please advise!

http://ww.wp.xz.cn/plugins/s2member/