Yes, all PC's are up to date.
See this thread;
any idea on how i can get this to work on xp pro? i installed the stand alone samsung driver (not kies) and when it's connected via MTP, i can only transfer media files and not regular files.
EDIT: i got it to work by simply upgrading my windows media player to ver. 11 in case anyone else runs into the same issue as me.
If the machine with the issue is on WMP 10 then try upgrading to WMP 11.