You should try upgrading to Melodyne 4. You should also verify that you are running Studio One version 3.3.4 or above as there was an issue that was resolved in that build. 3.5.2 is the latest build of Studio One 3.
Another possible issue is that you have used too many instances of Melodyne in the song that will not load. It is best practice to edit with Melodyne and then render your track to remove the plug-in. If this is the issue, you will want to go into Studio One>Options>Advanced>Services and disable the ARA service. You can then restart Studio One, open your song and remove some of your Melodyne edits. Finally, turn ARA back on, restart S1, and load your song.