Hdtv Problem

It would be greatly appreciated if someone could help with this i have a samsung hdtv its like 24 or 26 inches and whenever i watch hdtv channels or play my xbox on anything greater than 480p i get vertical lines that run accross the tv its kinda annoying i paid good money for this tv and this is ruining my experience and as i said this is only on hd channels i have comcast all non hd channels are fine i just recent changed my xbox360 from 480p to 1080i and they popped up as soon as changed:mad: any ideas or help would be great thankyou:helpme

*Problem solved*
i found out that my signal was being scaled up to 1080i when it needed 2 be on 720 so now the line is gone thanx anyway to the 50 ppl that viewed this and said nothing:mad: