divs in the feed?!

Hi all, I have a wierd issue with some divs that are included in the rss feed. As a result the feed does not validate.
I have the following in functions.php to display ads between posts:

/**
 * Insert banners between posts /tsl
 */
function ad_after_post_1( $post ) {
        global $wp_query;

        // Check if we're in the main loop
        if ( $wp_query->post != $post )
                return;

        // Check if we're at the right position
        if ( 1 != $wp_query->current_post )
                return;

        // Display the banner
                echo '<div id="inlinead">
                <script type="text/javascript"><!--// <![CDATA[
                        OA_show(1163);
                // ]]> --></script>
                </div>';
}
add_action( 'the_post', 'ad_after_post_1' );

function ad_after_post_2( $post ) {
        global $wp_query;

        // Check if we're in the main loop
        if ( $wp_query->post != $post )
                return;

        // Check if we're at the right position
        if ( 2 != $wp_query->current_post )
                return;

        // Display the banner
                echo '<div id="inlinead">
                <script type="text/javascript"><!--// <![CDATA[
                        OA_show(1164);
                // ]]> --></script>
                </div>';
}
add_action( 'the_post', 'ad_after_post_2' );

function ad_after_post_3( $post ) {
        global $wp_query;

        // Check if we're in the main loop
        if ( $wp_query->post != $post )
                return;

        // Check if we're at the right position
        if ( 3 != $wp_query->current_post )
                return;

        // Display the banner
                echo '<div id="inlinead">
                <script type="text/javascript"><!--// <![CDATA[
                        OA_show(1165);
                // ]]> --></script>
                </div>';
}
add_action( 'the_post', 'ad_after_post_3' );

Error on feedvalidator.org is:

line 39, column 1: Undefined channel element: div (3 occurrences) [help]

<div id="inlinead">
^

Removing the code from functions.php makes the feed validate...so I think it's not any plugin issue

Any help is much appreciated

Thanks