When crossing major version boundaries *always* upgrade to the .0 release first, before going to the last .x release. That's the *only* method that is supported and guaranteed to work. Going from X.y to A.b will almost certainly failed (as you discovered).
Doesn't anyone read what I post anymore?
I mentioned this at the beginning of this thread.
To upgrade from 5.x to 6.x you *have* to go to 5.5, then 6.0, then 6.whatever.