I am no longer able to use a custom form in Outlook 2003. I am sharing
contacts, from an additional contact folder (not the default Contacts folder)
with another user, when that user attempts to open the contact, which has a
custom form, Outlook repsonds with "The custom form could not be opened.
Outlook will use an Outlook form instead. The form required to view this
message cannot be displayed."

When I first set the share up Outlook seemed to download the form from the
Original Owner of the shared folder and display it, but the following day I
got the message above. The contacts still appear in the contact window when
you click on the folder, it is just that you can not open the contact to view
the details.