Do you have the DVDP setup right? It needs to be set to 4:3 WS or 16:9 WS depending upon which type of display you have.
Cast Away is flat (1.85:1), so if you have a 4:3 display, and have the DVDP set to 16:9, it'll look like it's playing in FS, but everything will be stretched vertically.
So it might be the player is set to the wrong type of output for whatever display you have. Or you might've gotten a FS disc in a WS package. Have you tried the disc in a different player/setup?