Grand Dad
It seems there is a fix for that message for windows 7 which can be downloaded:
http://support.microsoft.com/kb/969168
Hopefully after you download you'll be able to export your contacts
This article describes a message similar to, but not quite the same as, the message you describe:
http://support.microsoft.com/kb/301990
If that is the correct message, perhaps somebody could find the file described and send it?