Cartpauj & iComNow

i've got a problem with mingle forum...

if i activate the mingle forum plugin,
then my custom modrewrite dont work.

in my theme functions.php i've got the following code:

// here we register the variables that will be used as parameters on the url
function add_my_var($public_query_vars) {
    $public_query_vars[] = 'shopname'; // shopname
    $public_query_vars[] = 'shopcat'; // shopcat
	$public_query_vars[] = 'shopsubcat'; // shopsubcat
    return $public_query_vars;
}
add_filter('query_vars', 'add_my_var');

// building the rewrite rules, for the two parameters
function do_rewrite() {
     add_rewrite_rule('(shop)/[/]?([-a-zA-Z0-9]*)[/]?([-a-zA-Z0-9]*)[/]?([-a-zA-Z0-9]*)[/]?$', 'index.php?pagename=shop&shopname=$matches[2]&shopcat=$matches[3]&shopsubcat=$matches[4]','top');
}
add_action('init', 'do_rewrite');

if the mingle plugin is deactivate, its work.
if i active it, the rewrite in my functions.php dont work....

any idea?!