I did some tests last weekend with my gallery and (old) posts linked to it: Seems to work for most of mine. Not all. I don't know the different behavior.
Links not working, 2 different examples:
Link to old post
-->
Wrong/old link to gallery in this post
-->
This would be the correct one, I suppose
Link to old post
--> Image link appears as text-only-image inline. Without URL! Cannot be clicked, last example: SML_U41720I1307096436.SEQ.0.jpg
--> But the image # in the thread is correct, though just an image, not text. Changing the prefix SML to new MED works).
Here is the correct link, made manually by me using the text-only information of this specific case
Maybe this further information gives you some hints for a bulk correction.
Thank you anyway for all your effort up to now: The speed-up of the forum is a BIG WIN!