The 'sys is undefined' message occurs when the client side Ajax library cannot be loaded. This is beause a script handler is missing from the web.config file.
Found a solution to this problem for my site (version 1.9). I had the exact same issue with global settings page not displaying any settings even though with view source I could see the html was in there. Also I was not able to edit any pages in Content Management / Topics.
The site has always worked fine on my local machine. When I copied it to maximumasp (my hosting provider recently changed its name to CBeyond Cloud Services) I encountered the problem.
The issues was to do with session state management in a multi server hosting environment (cloud). Nothing inside a form was displayed. In my case, the hosting provider supply their own tools and instructions for setting up a session state database in sql server. After following their procedure the site now works.
This had to be added to <system.web> in web.config.