OK, I got a little further. In the cs_PostAttachments Table the Filename Value was 'IMG_1178', in the Storage Folder though it's filename is '1000.7.62.IMG_1178'
When I rename the FileName value in the cs_PostAttachments to 1000.7.62.IMG_1178 I don't get the error thus a red X instead of the Medium Size Image. Clicking on Original Size does not show the picture, renaming it back in SQL to IMG_1178 it show the Original Size Picture but not the Medium Size one.....
I know a bit confusing, but really not sure how this could have happened.
Works fine on 2.0, the only difference this Album has to any other, is that it has a parent Album...