With your encouragement, I decided to start over with a fresh copy of the files from the old server. I uploaded the files to the new server and checked all permissions: all looks okay (permissions are correct for phpsuexec).
At first, the UDM menu showed as a long unordered list of links, all expanded. The menu does not 'flyout'.
I think the problem is that the paths have changed from the old server to the new server.
Old server: http://www.example.com/index.htm
New server: http://serverbox.hostingsite.com/~example/index.htm
Because of this I am unsure how to set the lines:
$config = $_SERVER['DOCUMENT_ROOT'] .
in udm-dom.php and udm-style.php
Original setting of the above lines is:
$config = $_SERVER['DOCUMENT_ROOT'] . '/udm-resources/udm-custom.ini';
and the line:
Original setting: $um['baseSRC'] = '/udm-resources/';
And perhaps there are other lines I need to change to get the UDM menu to work correctly? Thank you so much for your help.