Did you try it from the destination server? As mentioned above, this is probably related to using older management server software to perform the copy. Try it from the 2012 server, it seems logical that the 2012 management software should be backwards compatible with copying data from 2005; but 2005 might not be able to copy data to a 2012 instance.

Please post back if you find a solution; so far we're working in speculation only.