The social buttons where never added to content when is_admin() == true -- before I added those sharing buttons on the Edit Post/Page. When I added those sharing buttons, the test for post_types was bypassed. I've corrected the code in the latest DEV version. Install this version, and let me know if it fixes the issue (it should). http://downloads.wordpress.org/plugin/nextgen-facebook.6.15dev4.zip
To install the archive, you can find instructions here:
If you downloaded the NGFB Open Graph+ plugin as an archive file -- either the Pro version or other GPL versions from WordPress.org -- follow the Automated Removal (if NGFB Open Graph+ is already installed) and the Semi-Automated Install methods to remove, install, and activate the new plugin. Please take care to check the "Preserve on Uninstall" option on the Advanced settings page before removing the plugin (as explained in the Automated Removal procedure).