Re: Is there a way for an disabled account to be reactivated by the administrator?
I don't think there is an application level way to do this. Maybe Tiki will reset after some interval but I do not know that. I'm no genius (as is obvious) but when things like this have happened I've gone poking around in the underlying MySQL database and made value changes in the appropriate fields. You obviously need access to this in your server's control panel.
I'm sorry I can't tell you what fields and in what table you'll find them. I have always had to go exploring to find what I need to change. I'm sure though that if you got in the database you could find it and change it.
Otherwise, as a clunky workaround, I have simply deleted users and then had them re-register.