DVD-player

[Hamram]

I have a few dvd-folders on my harddisk, and It was no problem to watch them before. Somewhere along the road is has started to be sluggish and malfunctioning. If I try to play off one of the dvd's now, I can open the folder, and the dvd-menu appears, but I'm unable to scroll through the menu and choose subtitles or even hit "play". That is, sometimes it is possible if I wait for like 5 minutes. Yesterday I managed to start a movie, but didn't finish it. Today the DVD-player didn't cooperate at all, so I was unable to finish the movie.

Any advice..?