I'm trying to change the default post thumbnail size to 235px x 235px and crop the image to fit exactly. I've tried changing the functions.php in multiple ways (set_post_thumbnail_size, add_image_size, through the settings, etc.), and so far, the only way i can get the thumbnail to 235x235 is through the css, which then pixelates the image. Any thoughts/solutions?
Try this plugin to regenerate your thumbnails. http://wordpress.org/extend/plugins/regenerate-thumbnails/