It seems that the Access Front end must be local to force absolute path definitions. If it is on the network then it insists on using relative locations (kinda makes sense if you read all the blurb).
I have 'discovered' this by dragging and dropping a file onto a hyperlink field, and then wishing to copy the file in the after_update event. The copy is via FileSystemObjects CopyFile method which always wants absolute paths (of course). My database (2007) was on a network share and always threw 'path not found' for the source file...until I moved it to my PC.
HTH anyone who's been fumbling around looking for a solution