Where are you trying to load them? Any custom races you've made should simply appear in the opponents list at the last page of new game creation. Note that if a customized race is based off one of the core races and not the actual "custom race" that you can only have one opponent based on that race in the game at a time. If they're based on the actual Custom Race race, you can fill the game up with them.

Custom race files are stored in My Documents\My Games\Gc2TwilightArnor.

Ah, that's where they're hiding. Ok, I ended up deleting all of the race config files,  starte the game, made a new opponent (based of a core race to clarify, sorry), the game CTD'd, restarted the game and haven't had any trouble since. :shrug: The custom opponents made from in-game are showing up now.

Thanks for the help!