Forum Moderators: mack
Chose one (probably the .com) as the actual site, and make a "Permanent Redirect" in your webserver from the other one to the main one. This way you should be on the safe side.
What you can do it use a redirect to point everything to your prefered choice of domain. From there Google will detect the duplicate content and will only pay attention to one of your domains. The one with the most inbound links will be the main site and Google will ignore the other.
It is impotaint to ensure you do nothing to promote the other domain. Simply point it to the other domain using an htaccess perm redirect and forget about it.
Mack.