I have the same problem as http://en.forums.wordpress.com/topic/image-size-shrink?replies=2#post-1253895 . My page shows my tiled (rectangular) galleries with very small images when not logged in to WordPress, but when logged in it looks fine.
I haven't seen this behaviour before, but then it's not often I'm not logged in to wp. Noticed the problem today because I booted up my new laptop, so at first I thought it was a problem in Win8/Chrome but since it disappears when I log in it shouldn't be.
The blog I need help with is gullmars.se.