OK - the attempt to import the previous accounts didn't work on first go - the email addresses didn't get pulled in correctly and this system doesn't allow anything if the email addresses aren't valid. If the email address wasn't correct then it wouldn't let you modify your account. And you couldn't create re-register under that name because the account was there - in theory (though non-functional). So rather than attempt the import again I just decided to delete all 3500+ old accounts.
So now you can register under your name of choice.
I will update the CRG Forum link to note this, but meantime please notify people via post on Team Camaro, as well as any of your buddies that might be interested, that the new CRG Forum is now accepting new registrants.