Some important things to note for versions 3.0 and below:

• The script that creates the images for the featured section and thumbnails requires the GD library, which is available on any host sever with PHP 4.3+ installed.
• Once installed and in-use, the script will automatically create a "cache" subfolder with proper write-permissions in the "scripts" directory of the theme. If your host server doesn’t allow this by default, be sure to manually change the "cache" and "scripts" folder permissions to 777.
• In addition, make sure the "scripts" directory is set to 777
• The slider uses the first image uploaded to the featured post. If you uploaded an image and decided it wasn’t the right one, or it was corrupted, be sure to delete it before or after you upload the next image.

NOTE: Some users have experienced issues when using images that are extremely large. Please make sure that you properly prepare images for the web and make sure they are not too large in file size.

If you continue to have issues (99% of the time it's hosting related), here is a link to the forums for this script: http://www.darrenhoyt.com/support/forum.php?id=4