I think it may be because you are using php 4.x
Upgrade to php 5
I had that error and this is what I did
Open /libraries/joomla/application/pathway.php
Replace the line at 209 with:
if((version_compare( phpversion(), '5.0' ) < 0)) {
$item->name = html_entity_decode($name);
} else {
$item->name = html_entity_decode($name, ENT_COMPAT, 'UTF-8');
}
so that the whole function looks like:
function _makeItem($name, $link)
{
$item = new stdClass();
if((version_compare( phpversion(), '5.0' ) < 0)) {
$item->name = html_entity_decode($name);
} else {
$item->name = html_entity_decode($name, ENT_COMPAT, 'UTF-8');
}
$item->link = $link;
return $item;
}
This describes the modification:
http://docs.joomla.org/Why_do_I_get_the_message_%22Warning:_cannot_yet_handle_MBCS_in_html_entity_decode%22
