Support Forum

OK - I removed the code after looking at it. It is nasty and totally goes against the WP coding rules. The good new is that it should be easy to fix up.

Locate the file membersonic.php in the wp plugins folder under membersonic.

Find these lines of code:

function wp_sm_get_header() {
    // load script
    wp_register_script('wp_sm_front_end_script_custom', plugins_url('/js/jquery-ui-1.7.3.custom.min.js', __FILE__), SM_VERSION);
    wp_enqueue_script('jquery');
    //wp_deregister_script('jquery-ui-core', 'jquery-ui-dialog');
    wp_enqueue_script('wp_sm_front_end_script_custom');

and change it to be like this:

function wp_sm_get_header() {
    // load script
//    wp_register_script('wp_sm_front_end_script_custom', plugins_url('/js/jquery-ui-1.7.3.custom.min.js', __FILE__), SM_VERSION);
    wp_enqueue_script('jquery');
    //wp_deregister_script('jquery-ui-core', 'jquery-ui-dialog');
//    wp_enqueue_script('wp_sm_front_end_script_custom');
    wp_enqueue_script('jquery-ui-core');
    wp_enqueue_script('jquery-ui-dialog');

Check to see if the forum page is working.

This wont be the end of it as that file you posted has some other libraries embedded in it but it is the place to start. So this might still error (the php code for this plugin is a bit of a tangle to be honest) but we can fix that when we see the result of the above. However - it would be useful if I could get to the forum page ion your site. at the moment I am getting 'Sorry. You don’t have access to this page. Please register and request permission to view it.' even when logged in with the credentials you supplied.

Well hat sounds promising.
Remember there may be some other, non-forum related things that don't work as they should. If you find any come on back and we can track them down and load the support script properly.
I would let the membership guys know we have made this change and why as well. And why we recommend using the proper WP api for these scripts.