The path is actually correct and the module has been running correctly for months until this update. I've posted on the civicrm forum but haven't gotten anywhere. So, I am casting about for ideas. There are other applications on the server (x-cart, slideshow director) that are also having problems finding their files.
Seems clear that this is not a CiviCRM issue nor even a Drupal issue. If the other packages also can't find files, then either it's a PHP bug or something changed between the old version and the new version. Without access to a system set up precisely as yours, it will be difficult to guess what's wrong--it could also have to do with system settings or other software/modules installed on your server.
If it were me, I would choose one of these packages and start playing with the code to determine where the path is getting lost. This
echo $variable_x;die;
while ugly, works quite well in such a situation--keep sticking that in different places until you figure out what's happening.
HTH