I have thumbnails setup to 85x85 cropped.
I have rebuilt thumbnails with 2 different plugins with the same result.
The thumbnail images are properly changed and cropped to 85x85.
However when I use
<?php the_post_thumbnail('thumbnail'); ?>
it returns results in the 85x85 image being stretched to 85x57 or 56x85.
In short, the thumbnails are being created properly but displayed as if they are not cropped.