I tried with various browsers on various operating systems and the subtree sometimes shows up and sometimes does not. I can't pinpoint what exactly causes the change in behaviour. I downloaded and diffed the html from the same page on a browser where I got to see submenus and one where I didn't and... there is no difference, apart from the random hashes. I suspect the javascipt is not being accepted. In the dev-console I got these error messages:
jquery.treeview.js?303:256 Uncaught ReferenceError: jQuery is not defined at jquery.treeview.js?303:256
(anonymous) @ jquery.treeview.js?303:256
SelectCategory.js?303:1 Uncaught ReferenceError: $j is not defined at SelectCategory.js?303:1
(anonymous) @ SelectCategory.js?303:1
I hope someone can fix this.