Pokemon Black keeps freezing?

My black version will freeze when the screen fades to black to raise N's castle from the ground. I have not used any cheats, like AR, etc. I was also having the same problem with Elesa lowering Driftveil Drawbridge, but it stopped freezing after I restarted a couple of times. I've tried taking out and reinserting the game card and doing soft resets, but each time it stayed frozen on the white transition screen.