It wasn't clear if the lines were still there after the first screen was replaced. I have seen plenty of screens with vertical or horizontal lines and even slices or half the screen missing that were the result of a damaged LCD.
I don't totally understand the 5x thing, but I would have at least tried for a second one if it didn't cost me anything. I'm sure everyone who replaces LCDs on a regular basis has had at least one that either isn't a direct replacement or was damaged in shipping. I actually had one that was U-shaped when I received it.
If the lines are still there I would think it must be a bad GPU. I had a DV2500 that looked like 8-bit color. I would have thought a driver problem (probably didn't help that I had another system in the same week that was due to the wrong driver being loaded) or bad screen for sure, but only a new mobo fixed it.
I'm not trying to be argumentative, just laying out my thought process (however right or wrong) when I run across this type of problem.