goto email accounts, view/change address books:
then delete the address books that are there (dont worry, this does not delete your info)
exit outlook
restart outlook
then goto email accounts and add new directory or address book. Add additional address book. then add the outlook address book.
You will need to restart outlook.
Try that, it is a fiddly proccess which doesnt always work first time (for some reason).
For more info, this is mentioned in the outlook help files.
best of luck