I noticed this problem before but it seemed to "go away" on it's own and I discovered the issue. I've just moved hosting companies - all seems to be back up and running as normal - except the styling of the Amember admin area seemed to be "wrong". It turns out that the SSL certificate hadn't been setup yet, and because of that the stylesheets are getting messed up somehow (probably not being called by browser due to mistrust issue or similar). Once SSL was up, all is good. Anyway, it had me puzzled for a bit until I figured it out, so posting here to save anyone else hitting this some head scratching