Hi Temuhin,

Go to Tools Option in Outlook > Options > Click on E-mail Options > Advance Email Options and click on the check box Suggest names while completing To, CC, and BCC fields. If the check box is already ticked then you will have to delete the NK2 file from C:\Documents and Settings\Your Profile Name\Application Data\Microsoft\Outlook\ there would be a file having the same name as your Outlook profile name usually "Outlook" which would have the extension .NK2. Try deleting the file. While deleting the file the outlook should be closed. Delete the file and then re-open the outlook and check. Let me know if this resolves the issue. Also if the issue is resolved then let me know which method worked the first one or the second one.