Wordpress - wp_enqueue_script adding conditional statement not working

From quick look at code this conditional only seems to be processed for styles and not scripts.

It is a long shot, but you might try registering the script, then adding in the conditional, and then enqueueing the script:

// Register the script
wp_register_script( 'dd_belatedpng', get_stylesheet_directory_uri() . '/js/dd_belatedpng.js', array(), NULL, true );
// Attempt to add in the IE conditional tags
$wp_scripts->add_data('dd_belatedpng', 'conditional', 'lt IE 7');
// Enqueue the script
wp_enqueue_script( 'dd_belatedpng' );

I don't know that it will work, though

EDIT

Based on the related Trac ticket, it appears $wp_scripts doesn't support this method.

You may just need to pull the script out of the wp_enqueue_script() system, and echo the IE conditional-enclosed script call inside of a pluggable function hooked into wp_print_scripts or wp_head. It's certainly not ideal, but if this is a single-use client Theme, then you don't have to worry about someone else needing to deregister the script.

This is the work around I had to put in place since WP doesnt support what I was trying to do

functions.php

add_action('init', 'sort_out_jquery_pngfix_frontend');
function sort_out_jquery_pngfix_frontend() {
    if(!is_admin()) {
        wp_deregister_script('jquery');
        wp_register_script('jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js', array(), NULL, true);
        wp_register_script('dd_belatedpng', get_stylesheet_directory_uri() . '/js/dd_belatedpng.js', array(), NULL, true);
    }
}

add_action('wp_print_scripts', 'register_theme_scripts');
function register_theme_scripts() {
    if(!is_admin()) {
        wp_enqueue_script('modernizr', get_stylesheet_directory_uri() . '/js/modernizr-1.7.min.js', array(), NULL, false);
        wp_enqueue_script('googlemaps', 'http://maps.google.com/maps/api/js?sensor=false', array(), NULL, true);
        wp_enqueue_script('jquery');
        wp_enqueue_script('sc_wc_js', get_stylesheet_directory_uri() . '/js/function.js', array('jquery'), '1.0', true);
    }
}

footer.php

<?php wp_footer(); ?>
<!--[if lt IE 7]>
<?php wp_print_scripts(array('dd_belatedpng')); ?>
<script>DD_belatedPNG.fix("img, .png_bg");</script>
<![endif]-->