Cached user info?

I found it necessary to change the GID of a POSIX group defined in LDAP. But when I log in with a user that is a member of this group, I find that the user's group membership still reflects the old GID.

At this point, I've tried removing the user from the group, and adding it back--it still comes up with the old GID when logged in (or, specifically, typing "groups" at the command prompt lists a group associated with the old GID), even though I can't see *anything* referencing the old GID in the LDAP database.

I am stumped. Anyone have ideas about what might be going on here?