The image sizes are generally supposed to be 264 by 200….which is controlled by the image size set inside your functions.php file – “add_image_size( ‘portfolio-thumbnail’, 264, 200, TRUE );”
You may just need to try a plugin called Regenerate Thumbnails – http://wordpress.org/extend/plugins/regenerate-thumbnails/ and run it to see if it adjusts everything automatically (it should).
This is what nearly all Genesis Developers (as well as other WP users) use to adjust image sizes. Anytime you add, remove, adjust an image size, its best to use a plugin like this since it will go through and adjust all of your images automatically to the size you have specified in your theme. You can read up on how it works on the plugin page, but all you really need to do is download it and run it and everything will be done instantly. You only need to run it if you change an image size….this works for sliders and pretty much any part of your theme that uses thumbnails.
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