If the user cannot access their local contacts when attempting to send an email message the problem may be that their Outlook Address Book account has been removed.

To resolve this issue:
Within Outlook go to Tools > E-Mail Accounts
Under Directory select View or change existing directories or address books, click Next
If you do not see any address books listed on the Directories and Address Books screen you will need to add one

To add the local contacts as an Outlook address book:
Within Outlook go to Tools > E-Mail Accounts
Under Directory select Add a new directory or address book, click Next
Select Additional Address Books
Outlook Address Book
You will have to restart Outlook before the change you will be able to see the address list.  (It may take a few minutes for it to full appear)