cached credentials

We have UserA logging on to a W2k domain. This user can browse and connect
to all domain resources, except for shares on a single server, \\server.
When this user tries to connect to any resource on \\server (or even perform
a net view \\server), a dialog pops asking for password for a different user
(UserB). If you cancel the dialog, access to the resource is denied to UserA,
even though the user has full rights on the resource. At some point in the
past UserB must have connected to a resource on \\server while UserA's
profile was loaded. But we cannot figure out how to clear these cached
settings without rebuilding UserA's profile (which is a lot of work). Any
help out there? Thanks in advance. Chuck