INJ and REM files are a means developed by DAZ - not by Curious Labs - to allow an astonishing range of morphs while keeping the file size (in most cases) to something workable. They do work in Poser 5; however, it has been noticed that they only work properly if the figure and INJ/REM files are installed in the same Runtime as Poser 5's directory - that is, the "default" RUntime that Poser creates. From the sound of things, this may be your problem, since it's having trouble finding the files.