The error message goes something like this: "The path is too long after being fully qualified".
If you can't rename your folders or map a network drive to shorten the path, FORGET IT. This problem has been around for years and still hasn't been fixed. It will most likely never be fixed.
A couple of alternatives from the top of my head: rsync and robocopy. Here:
Rsync howto and alternatives.
They are not as cute as Synctoy but, on the other hand, they are not toys and will get the job done.