You can edit the names directly in the customerace.xml which will be located in your:
Documents\My Games\GC2DarkAvatar folder.
This may or may not fix your bug, sounds like you may have messed with the planet naming in the xml previously and might have borked it a little.
Create any other custom race and save it (different name to what you are using) and compare the two to see if your current file has errors.
Notepad++ is a fine xml editor.