Account lockouts

I have had trouble with this for several months and liaised with other administrators, Microsoft technicians themselves, and read all the articles. No answers yet!

IT infrastructure: 2 w2k sp1 dc's, 2 w2k sp1 member servers. Native mode, Exchange 5.5 sp4 on one member server, Clients 95, NT4 and W2k Pro. Servers time is in sync. ADC installed between Exchange and W2k.

Problem: When the client is forced to change password at logon, it opens Outlook and an authentication box pops up with Username, Password and Domain name. Neither the new nor old password is accepted. The user account in AD is then locked out.

Errors on Exchange box: failed: logons source: system reason: 50% of the time "The netlogon component is not active" otherwise just "bad username or password"