After refactoring from eZP 2012.6 to 2012.8 a setup that uses several eZP installations linked to a central one doesn't work as it should anymore. The problem is further described here:

http://share.ez.no/forums/developer/problem-with-linked-installations-after-2012.8

The source of the problem is the usage of the _DIR_ PHP magic constant, so this part should be refactored somehow.