A misconfigured Outlook Address Book service would cause that.  Click
Tools>E-mail Accounts>View or change existing directories or address
books>Next.

If you see Outlook Address Book listed, select it and click Remove.  Stop
and restart Outlook.  Then click Tools>E-mail Accounts>Add a new directory
or address book>Next.  If you don't see it, click Add.

Choose Additional Address Books and click Next.  Select Outlook Address Book
and click Next.  Specify the remaining information, like sort order, and
click Finish.  Stop and restart Outlook.  Then, check your Contacts
properties as I described int he prior message.