I Dont know why, but after integrating gallery2 into joomla 1.5 the pathway-links had an parameter of ?g2_GALLERYSID=TMP_SESSION_ID_DI_NOISSES_PMT, which looks baaaad ;)

so the dirty way to get rid of that tmp-session-stuff is simply to replace that string with "nothing".

Open [YourJoomla1.5Installation]/libraries/joomla/application/pathway.php in a text-editor of your choice and look out for:

if ($this->_pathway[] = $this->_makeItem($name, $link)) {

(should be around line ~167, just look around - it's the function "addItem")

$link = str_replace("?g2_GALLERYSID=TMP_SESSION_ID_DI_NOISSES_PMT","",$link);

function addItem($name, $link='')
{
// Initalize variables
$ret = false;
$link = str_replace("?g2_GALLERYSID=TMP_SESSION_ID_DI_NOISSES_PMT","",$link);
if ($this->_pathway[] = $this->_makeItem($name, $link)) {
$ret = true;
$this->_count++;
}

return $ret;
}

That's it, have fun!