samba - Nov 2001 - Encrypted Passwords via Win 2000 PDC not consistently being passed!!

We are using a windows 2000 server to pass encrypted passwords to our samba
server. It has joined to the PDC as a memeber server and it works, except
that 1 out of four times our login script still asks for the second password
before allowing the mapping of the drive to the server running samba

Anyone know why this is happening.

Thanks
Greg turnbull