Hi,
If you store contact information in outlook data file(.PST), the outlook data file(.PST) might corrupted, please try to create a new outlook data file(.PST) test if it helps.
If the problem does not appear, you can use scanpst.exe tool repair old outlook data file.
" How to find and run the Inbox Repair tool in Outlook"
http://support.microsoft.com/kb/272227
Or transfer outlook data, please see: "How to manage .pst files in Microsoft Outlook"
http://support.microsoft.com/kb/287070
Best regards.
William Zhou
TechNet Community Support
