Date: 2011-08-22 09:30
Posted By: Ludger Merkens (lume)

same problem here. 
manually changing the browsers charst to utf-8 fixes this. It seems as if
somwhere in the process ISO-8859-1 headers are sent, as even adding <meta
http-equiv="Content-Type" content="text/html;charset=UTF-8"> to
templates/admin_printinvoice.tpl won't fix the problem. (As a sidenote:
$config['admin_encoding'] = 'utf-8';)