Running Exchange 2003.  This issue happens in both Outlook 2000 and 2003.

We have several distribution lists setup in a public folder.  This lists
will no longer update.  We've made several changes to individual contacts in
the folder.  When we get into each distribution list and hit the "update now"
button nothing changes.  Members of the list with known changes maintain
their old data even though their entries in the public folder have been
changed.  When this distribution list is used, email is sent to the old
addresses.  How do I correct this problem?