[Fri Sep 04 03:50:36 2009] [error] [client 77.224.234.184] WARNING: 2009-09-04 03:50:36 (CEST): "htmlentities() [<a href='function.htmlentities'>function.htmlentities</a>]: Invalid multibyte sequence in argument" in file /var/www/red/views/default/canvas/layouts/widgets.php (line 164),
 referer: http://artelibredigital.net/red/index.php

Line164:

<input type="hidden" name="description" value="<?php echo htmlentities($widgettypes[$widget->handler]->description, ENT_QUOTES, 'UTF-8'); ?>" />

Everything points to a problem of PHP with UTF-8:

http://lists.nyphp.org/pipermail/talk/2008-January/024663.html
http://www.phorum.org/phorum5/read.php?61,131083
http://www.phpwact.org/php/i18n/utf-8

Spanish translations use accents... solution?

Delete [htmlentities]

;)