[wp-hackers] Featured image functionality dissapeared from custom post types after upgrade

[andre at pixelplexus.co.za]

Hi

I see a couple of mentions of similar problems on the forums but no detail
of what the problem might be or how to fix. So asking here and will start
digging.

A site that uses featured images on a custom post type. After upgrade to
3.4.1 when you go to the edit screen for *some* of the custom posts, the
featured image is no longer set. If you click on set featured image there
is still an image listed in the 'gallery' tab. However there is no 'set as
featured link' and the image thumbnail seems blank. Full size lists the
image size as (0 × 0). (so suspect something broken in the db :-| (Got
exactly the same result on a clone of the site)

Will go through disabling all plugins etc. but its weird that it was
working perfectly before the upgrade.