stereo not working

While i was wheeling the other day, i had my aftermarket stereo off, hit a root and all of the sudden the display screen shut off and it started making the beep noise like the car is turned off b/c i left the faceplate in. Took the stereo back and got a new one, and when i plugged the new one in it started beeping again with the car on. So, i guess i'm trying to say the stereo thinks the car is always off. There is still power to the stereo b/c i can put in and eject cd's. Any ideas?

there are 2 hots one for the clock and one for power but as a quess id quess a bad ground run the wires back to the fusebox or batt till you get the one that fixes the prob than go from there