There's two ways to generate thumbnails in a theme:
1. Use a script like TimThumb to resize it when the picture is loaded (what your theme uses).
2. Allow WordPress to resize it when you upload the image, and then deliver that image.
I'm not sure the specific reason why your images aren't resizing but it's something to do with TimThumb. For example, when I visit this link: http://worldbestsports.com/wp-content/themes/Zenko Magazine v1.2/scripts/timthumb.php?w=235&h=140&zc=1&src=http://worldbestsports.com/wp-content/uploads/2011/02/new_york_mets-300x240.jpg
I get an error. It might be because there's spaces in the name of your theme directory, or it might be some other issue.
Rather than troubleshooting possible TimThumb solutions, I'd recommend just moving to the WordPress method.
1. Define the different image sizes you want in the functions.php file. For example, here's the two you might use, based on the images in the Baseball section:
add_image_size('home-featured', 235, 140); // scales the image to fit in a 235x140 box without cropping
add_image_size('home-thumb', 90, 70, true); // scales and crops to 90x70
More information here: markjaquith.wordpress.com/2009/12/23/new-in-wordpress-2-9-post-thumbnail-images/
2. Replace the timthumb image calls in your theme file with WordPress Post Thumbnal ones.
the_post_thumbnail('home-featured');
the_post_thumbnail('home-thumb');
I hope that helps.