New tv not working?!?!?

[POW]

I just bought a 42' vizio hdtv yesterday. this morning all of the stations were playing just fine, i left the tv on while i was gone and when i got back i had a black screen! i realized only about 10 channels out of 200 are showing a picture/show. whats wrong did i hook something up wrong, is it the cable box or did i get a bad tv?! help..thanks