You have probably solved this by now but since I have just had to resolve this problem myself, and in order to help anyone else with the same issue, here's what I did:
- Select 'Contact' by preference
- Press the Menu button
- Select 'Edit contact' from the options
- Wait for contact info to arrive then press Menu button again
- Select 'Separate' option
- Select 'Yes' option from dialogue box to confirm action
At this point, all duplicate entries will now appear in Contacts section.
- Select a duplicate entry
- Press Menu button
- Select 'Delete'
Do this for all duplicate entries.
In my case, this occurred when I had a replacement Android phone and had several back-up entries when data was transferred and also synced.