The section from lines 561 - 570 (the calendar and SMFShop) should look like:
// The [calendar]!
if ($context['allow_calendar'])
echo ($current_action == 'calendar' || $context['browser']['is_ie4']) ? '<td class="maintab_active_' . $first . '"> </td>' : '' , '
<td valign="top" class="maintab_' , $current_action == 'calendar' ? 'active_back' : 'back' , '">
<a href="', $scripturl, '?action=calendar">' , $txt['calendar24'] , '</a>
</td>' , $current_action == 'calendar' ? '<td class="maintab_active_' . $last . '"> </td>' : '';
//Begin SMFShop 2.0 (Build 8) MOD code
//loadLanguage("shop");
echo ($current_action == 'shop' || $context['browser']['is_ie4']) ? '<td class="maintab_active_' . $first . '"> </td>' : '' , '
<td valign="top" class="maintab_' , $current_action == 'shop' ? 'active_back' : 'back' , '">
<a href="', $scripturl, '?action=shop">Shop</a>
</td>' , $current_action == 'shop' ? '<td class="maintab_active_' . $last . '"> </td>' : '';
//END SMFShop MOD code
Replace your current code with that, and it should work.