Okay, the bad news for the original poster, myself and anyone else in this situation is, on advice from several others who have had the same issue in the past, the grey/coloured/white/black lines mean a logic board defect, which is very expensive.
If you're in warranty I guess you're in luck - I'd take the device in to Apple at the soonest conveniece. If like me the warranty just expired let's hope Apple take sympathy on you. For us Australia customers don't forget the ACCC has ruled that 'statotory rights are not limited to a set time period. [The ACCC] advises that they apply for the amount of time that is reasonable to expect a product to function properly, given the cost and quality of the item.'