Can 06 GB song worked on in GB 09 put back in GB 06?

I need to share a song I have been working on in my GB 06 with a MacBook pro GB 09, in order to finish it because mine is not working correctly. Tracks are disappearing, among other things. Can I bring it back into my GB 06 or should I save as some other type of file in order to bring it back to my computer. Also, how exactly do I get it to the other computer, through the drop box? I tried but it said the drop box was locked or there weren't enough privileges.