promblems with my lcd

wassup,

i am installing a dash mount 5" lcd in my 2002 kia spectra and having problems. i have everything hooked up right that i know of. i also took it to a local car stereo shop and it played the dvd perfeect with a flat screen look when he tested it in the store.

but when i hooked it back up in my car it continues to have an unclear picture and i dont have any clue why. its so unclear that i can only barely see the dvd loga at the begginning of my movie. i have the power hooked to the back of my sony cdx 7850 voiceguide cd player. and my ground is just a  regular ground in the dash. can u please help me to save me some$$$$$$$$$$$$.  do i need to move the batt or the ground or what do i have to do.

well the power and the rca wires come out of this box right next to each other.  but when i installed my tv it was just for testing and i ran in to problems. but i will try tat. Is there any specific lenght they need to be apart?