I have the following code in my functions.php file and am only running the akismet plugin, but the new image sizes are not showing up in the media upload area.
// Post Thumbnail Support
if (function_exists('add_theme_support'))
{
add_theme_support('post-thumbnails');
set_post_thumbnail_size(1280, 640);
set_post_thumbnail_size(640, 320);
set_post_thumbnail_size(160, 80);
}
// Add new image sizes
if (function_exists('add_image_size'))
{
add_image_size('Portfolio Thumbnail', 160, 80, TRUE);
add_image_size('Portfolio Large', 1280, 640, TRUE);
add_image_size('Portfolio Featured', 640, 320, TRUE);
add_image_size('Self Portrait (about sidebar)', 200, 233, TRUE);
}