I am having the same problem. Redirecting between the original subdomain back to the mapped domain only happens when logged in getting an Unknown key arror the follwing parameters are being passed:
?action=login&dm=1ba50ab52754c394be8d5f659ffda771k=84a8b1b13840bd30a9ac63e0b4403b91&t=1246379060

Was using version Version: 0.4.3 prior without problems.