Have you made any custom modifications or custom theme code that integrates with MyBookTable? MyBookTable recently underwent an update that changed some of it's interfaces and templating system. If not, are you sure you are running in Compatability Mode (found in the MyBookTable Settings page)? That can usually solve theme compatibility issues, though it's not clear why these issues would have just started cropping up now.
Could you link to the page that is displaying the problem? I'll take a look and see if I can give more specific advice on how to resolve this as quickly as possible.