Why does my dvd player with usb drive stop reading movies halfway through?

I have a Philips brand DVD player (DVP5990) with a usb drive in it which allows me to play movies/seasons from files on a thumb drive. Recently it has developed the habit of cutting out about 1 hour into the movie and refusing to play more (even if I fast-forward past that point, it does not work). This only happens for movies and not TV episodes of comparable length. What is wrong/what can I do/can anything be done? Thanks.