When you mapped, you probably mapped while you were
logged on to the network (with an account on the server),
then you re-logged on to the local computer (with an
account on the local computer); or you must have mapped
while logged on locally, then queried for credentials of
an authorized user within the domain... well, because you
are logging on to the local computer the mapped drive
will not be remapped because it require the credentials
of the original person (network credentials). Hope im not
confusing you. Note: make sure the box is checked
to "reconnect at logon." Good luck!