Contacts in Outlook 97

I have a user with the following problem:

She imported her contact list into Microsoft outlook. About 20% of the 700 contacts she has, cannot be opened or updated.The following error message appears when attempting to open a contact:

“Can’t open this item. Could not complete the operation. One or more parameter values are invalid.”

This also happens when Contacts are created manually. Any ideas what this message means?

canadianchick