See the following message & patch: http://osdir.com/ml/network.poptop/2006-12/msg00005.html http://osdir.com/ml/network.poptop/2006-12/txt3zTuL6C5hj.txt
There is no way of determining if a password is a NT hash or not - people could have passwords that could be mistakenly interpreted as NT hash and the patch will break pppd for them. Closed as WONTFIX.