Change the main.tpl in /extensions/rem_board_header/ to this:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" <!-- forum_local -->>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- forum_head -->
</head>
<body>
<div id="brd-wrap" class="brd">
<div <!-- forum_page -->>
<div id="brd-head" class="gen-content">
<!-- forum_skip -->
<!-- forum_title -->
<!-- forum_desc -->
</div>
<div id="brd-navlinks" class="gen-content">
<!-- forum_navlinks -->
<!-- forum_admod -->
</div>
<div id="brd-visit" class="gen-content">
<!-- forum_welcome -->
<!-- forum_visit -->
</div>
<div class="hr"><hr /></div>
<div id="brd-main">
<!-- forum_main_title -->
<!-- forum_crumbs_top -->
<!-- forum_main_pagepost_top -->
<!-- forum_admin_menu -->
<!-- forum_admin_submenu -->
<!-- forum_main -->
<!-- forum_main_pagepost_end -->
<!-- forum_crumbs_end -->
</div>
<div class="hr"><hr /></div>
<div id="brd-about" class="gen-content">
<!-- forum_about -->
</div>
<!-- forum_debug -->
</div>
</div>
</body>
</html>
Uninstall the extension, replace the extension files, then install again. Sorry for the mixup .
If you need any PunBB 1.2.* mods done, feel free to send me a PM; we can work out a price [if need be].