Image Thumbnail Media Settings Are Being Overwritten Somehow…

Hi. I have been researching for hours trying to figure this out: my featured image thumbnails are all different sizes. I need them to be smaller and all be the same width and height. I have tried adding in

// 50 pixels wide by 50 pixels tall, crop from the center {
set_post_thumbnail_size( 50, 50, array( 'center', 'center')  );

into my functions.php and nothing changed. I have also downloaded Regeneration Thumbnail, but again, nothing changed. I’ve also tried to use Firebug to find out what may be causing this problem, but still nothing. WordPress is obviously overwriting something, but I cannot figure it out. Please help!

My site is HERE Thanks!