Been upgrading to WP 2.5 and just now 2.5.1. But had the same problem since I change from 2.3 to 2.5.
The new imageuploader, and the corrensponding insert gallery or even insert image into post, always retuns with fullsize images in post.
Even though I still check the thumbnail/preview radio button before inserting into post.
I see some thumbnails beeing generated when I look in the folders, but it just don't seem to take use of them. my WP isn't made for images larger then thumbs, and it's mainly text, with some references to images with the help of thumbs and lightbox.
I see the class in the code is refering to "alignnone size-thumbnail wp-image-149" but the size function here isn't working for my sake
Anyone else with the same problem?
Take a look at http://husbygging.karianne-elise.no/ (the posts before 13 of april is older post made with 2.3.x and is working fine)