Calendar Sharing fails

Hello Everyone

I have an issue with Outlook 2000 on one machine. When
this user gives sharing permissions to other staff all
seems ok. The other staff accept her calendar updates,
then with no one doing anything, the owner sends out
another message that updates are no longer being sent,
and all members are removed from the list.

We are using Windows XP with NT Server. No other users
are having any issues. All are on the same network using
Windows XP.

I have tried nfclean.exe and I renamed and installed Net
Folders again. No changes.

Does anyone know what the problem could be?

Thanks
Nick