[Ted S]

When suppression is enabled the welcome headers won't appear on any showthread pages. Either your hack versions are not upgraded to the latest versions or there is some other code conflicting with the plugins.

if($vbulletin->options['lgvon'] AND !$vbulletin->options['wlhlgv'] AND (THIS_SCRIPT == 'showthread' OR THIS_SCRIPT == 'showpost' OR THIS_SCRIPT == 'printthread') ) {
    } else {
     eval('$welcomeheaders = "' . fetch_template('welcome_headers') . '";');
    }

What this code does is checks if LGV is on, and if so, if WH Supression is off and if so, if the script is showthread, printthread or showpost. If anything is changing any of these variables or the page names it won't work properly.