BuddyPress Activity Plus - FAILED - Internet Explorer Only...

Hi Guys, I recently upgraded BuddyPress, Wordpress and the BuddyPress Activity Plus plugin to their latest versions. Since then, members using Internet Explorer are unable to upload a photo using the Buddypress Activity Plus plugin. Essential, they get a 'FAILED' message appear after a few seconds rather than the intended photo. What's weird is this ONLY affects IE users, Firefox and Chrome both work as intended. Also, as a site admin testing this, it works under IE, but not for regular users.

I think I've found the cause of the error in my functions.php file, because if I remove the following code from it then it appears to work across all Browsers!!!

//Allows Only Admin To Access The Backend

add_action('init','no_accesss_for_others');

function no_accesss_for_others(){

    if(!(is_user_logged_in()&&is_admin()))
     return;

    global $current_user;

    if(is_admin()&&($current_user->user_login!='admin')&&!custom_is_ajax_request()){
        wp_safe_redirect (get_bloginfo('url'));
    exit(0);
    }
}

function custom_is_ajax_request(){
    if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest')
        return true;
    return false;

}

The above code only allows me as 'Admin' access to the backend of my site. This is essential for my site as I have other site admins that help me run it from the frontend. Obviously, I don't want them having access to the backend...

Any ideas please why this code no longer works with IE and the BuddyPress Activity Plus Plugin as this all worked just fine before I upgraded...

Many thanks
Rob.