[Dead Eddie]

Untested...so try it on a test install first:

PHP Code:

if(isset($_GET['letter'])) {
    $vbulletin->input->clean_GPC('r', 'letter', 'TYPE_STR);
    $letter = $db->escape_string($vbulletin->GPC['letter']);

    if($letter == '#') {
        $hook = " AND LEFT(thread.title, 1) BETWEEN 0 AND 9";
    }
    else {
        $hook = " AND LEFT(thread.title, 1) = '$letter'";
    }

    $hook_query_where .= $hook;
} 


Also, change the hook location in the file you've released to forumdisplay_query_threadid. That might solve some people's problems.