I'm afraid that there's nothing you can do about it. I had the same problem due to static electricity. I managed to get a new HU via my car dealer, I told him that the HU was defect, let him listen to the distorted sound, and he agreed that the unit was broken. Because my car was still under warranty I got a new HU for free. Perhaps you can try the same trick. Hope that he doesn't read this thread.
If you do receive a new HU and you still have the (oo) to try it again; make sure that you connect the ground on your DVD player first before you make any other connection to the HU. This works for me every time, my carPC is connected to a ground wire in my car and since then no more problems.