Problem with setting a cookie variable with a hook!

[Citizen]

I setup a sidebar for navigation on my forums. I want the sidebar to be removable if my users click a link at the bottom of the side bar. The sidebar works great, but if you click the "remove" link, nothing happens.

http://www.gunzfactor.com/forums

Hook Name: "Sidebar Cookie"

Hook Location: global_start

Hook Code:

$show['sidebar'] = true;

if ($_REQUEST['do'] == 'hidesidebar')
{
   vbsetcookie('hidesidebar', 1, true);
}

$vbulletin->input->clean_gpc('c', 'hidesidebar', 'TYPE_INT');

if ($vbulletin->GPC['hidesidebar'] == 1)
{
    $show['sidebar'] = false;
}

The template conditional:

<if condition="$show['sidebar']"> </if>

The "remove" link points to:

{$vbulletin->options['bburl']}/index.php?$session[sessionurl]do=hidesidebar

Any idea where the problem is?