My user-avatar.php came like the following.
function user_avatar_admin_print_styles() {
global $hook_suffix;
wp_enqueue_script("thickbox");
wp_enqueue_style("thickbox");
wp_enqueue_style('user-avatar', plugins_url('/user-avatar/css/user-avatar.css'), 'css');
}
I tried swapping out all 3 thickbox calls for prettyphoto, and i get the invalid url error.