[boatswife]

Find this in the product file

<title>VDB - usergroup options saving</title>
<hookname>admin_options_processing</hookname>
<phpcode><![CDATA[if (is_array($vbulletin->GPC['setting']['bbactive_groups']))
{
$vbulletin->GPC['setting']['bbactive_groups'] = implode(',', $vbulletin->GPC['setting']['bbactive_groups']);
}]]></phpcode>
</plugin>
<plugin active="1" executionorder="5">

and replace with this

<title>VDB - usergroup options saving</title>
<hookname>admin_options_processing</hookname>
<phpcode><![CDATA[if ($oldsetting['varname'] == bbactive_groups)
{
$settings["$oldsetting[varname]"] = implode(',', $vbulletin->GPC['setting']['bbactive_groups']);
}]]></phpcode>
</plugin>
<plugin active="1" executionorder="5">

It's the same as what's posted above, but easier to figure out. This is working fine for me in 3.8