on trying to create any sort of field in any User Form the attempt ends in a blank page at /admin/EditForm. This happens on PHP Version 5.2.10, Firefox 3.5. If you need further information, just ask for it ;-)
Have you recently updated the module from a 0.1 version? If you have make sure you flush your cache when you update - www.site.com/admin?flush=1 and check your browser is not caching any of the older js files.