UberCMS MDK's version is r51. And for this error cannot be fixed unless you know exactly what to do. I suggest you download a fresh Copy from a different source try Googling: 'How to setup UberCMS' so that they know it works so it will work for you.
It's due to Habbo deleting their old CMS style files. Only way to fix this issue is to have them hosted on your own site, or find a release where they are up to date.
Actually, just update web-build, but if there are no avatars, go into inc/tpl/ and comp-me, and do Ctrl + H, and find habbo.co.uk, and replace with Habbo.com matey!