Problem with iPhone LCD after repair
I had the same problem before, when I replaced a cracked iPhone screen for a friend. When a 3GS digitalizer gets in contact with an iPhone 3G LCD they send the wrong signals to the motherboard(through ribbon cable 3) and then the graphic part of the motherboard brokes. So you will probably have to replace the whole motherboard, be more careful when buying new glass next time, check the modelnumber first!