Do a file search for .pst files. It is usually in your user settings directory and should be outlook.pst. If you have alot of contacts in this file, make a backup but rename it something else. You can only have one outlook.pst file to function off of. First try the .pst repair:
http://support.microsoft.com/kb/272227/en-us
Did you repair Outlook?
Just to make sure you have your sync options checked in AS/WMDC on PC and on 6700, right? And you have AS/WMDC setup for USB, right? What versions are you using for Outlook and Windows?