domain mapping cache or cookie bug

http://www.beyourbody.com/
is domain mapped to
http://cre8tives.org

WHEN LOGGED IN, beyourbody will not load as its caught in a permanent loop of some kind.

Have seen this happen before. Was told to clear cookies to fix this. Now I'm reporting on it when it can be observed in action.

Support access is granted, so log in and watch the white screen of death.

P.S. This has happened about five times now on multiple domain-mapped sites. It is very difficult to have to explain to clients to clear their cookies every time this happens.