just looked at yours madLyfe and you have plenty of extra extensions installed. Can you try a basic Joomla 1.6.3 installation with just sample content and try MC on that? If there is no problem there then it's something related to one of those many 3rd party extensions.
I get the same error message, Here is what it says after I try to select it as my default. This is on a fresh Joomla 1.6.3 install. My other RT template (paradox) is working fine.
Fatal error: Uncaught exception 'Exception' with message 'XML file did not load' in /data/16/1/15/122/1830448/user/1985595/htdocs/libraries/joomla/form/form.php:1704 Stack trace: #0 /data/16/1/15/122/1830448/user/1985595/htdocs/administrator/templates/rt_missioncontrol_j16/lib/rtparameter.php(47): JForm::getInstance('templateDetails', 'templateDetails', Array, true, '//config') #1 /data/16/1/15/122/1830448/user/1985595/htdocs/administrator/templates/rt_missioncontrol_j16/lib/rtcore.class.php(80): RTParameter->__construct(Object(JRegistry), '/data/16/1/15/1...') #2 /data/16/1/15/122/1830448/user/1985595/htdocs/administrator/templates/rt_missioncontrol_j16/lib/rtcore.class.php(65): RTCore->getTemplateParams() #3 /data/16/1/15/122/1830448/user/1985595/htdocs/administrator/templates/rt_missioncontrol_j16/lib/missioncontrol.class.php(32): RTCore->__construct() #4 /data/16/1/15/122/1830448/user/1985595/htdocs/administrator/templates/rt_missioncontrol_j16/lib/missioncontrol.class.php(26): MissionControl->__construct() #5 /data/1 in /data/16/1/15/122/1830448/user/1985595/htdocs/libraries/joomla/form/form.php on line 1704
Grr, it's so frustrating because it's clearly something that you guys have in common, yet I can't replicate it at all.
FYI, i've tested locally and remotely with PHP 5.2 and 5.3, With older Joomla's that have been upgraded and also with fresh 1.6.3 installs. Still can't replicate. We'll keeping digging in....