PS3 Dark Knight stopping problem.

[Joker1525]

I got The Dark Knight on Blu-ray a week ago. When I put it in, it plays fine. Its plays great for about 45 minutes. Then it stops. I can bring up the control panel, but it wont let me do anything and I can use the play, FF, RW and pause buttonsbut the screen stays the same. I can quit playback, but it wont load ANY other discs or demos untill I turn it off and then back on again. If I try to turn it off the light on the front just flickers untill I turn it off manually. I have a 40GB PS3 hooked up with a new HDMI cable. Im pretty sure that its not the system because I've plaed Blu-rays on it before. But I also dont think that its the disc because it keeps doing it in different spots. And, sometimes it skipsfirst but sometimes it just stops out of no where. I bought it used at Gamestop in January so I dont think I have a valid warranty anymore.

I really dont know what to do