Hi Aussiephil,
First of all, i appreciate your hard work your are doing with your RGB led

Very nice and <res. for your controllers made....
for the DMX, i think, the best way is to delete the actual ones, reboot the system, re-install and check again... But i'm sure you do it yet....
Another issue, is to check your Bios, if there is not somehing disturbing the com ports...
Last issue is to declare another com port available too and you change it...
Let me know your advancement status...
Wich DMX controller are you using ?
Cheers, Henri