What you are describing here is actual consistent with that of a LCD panel failure. This is not good news, because the LCD panel if available is always more money than just purchasing a new set. I wish I could see it for myself so I could be 100% sure but from your description I am about 95% sure that what you are describing is a bad LCD panel. Especially if the problem only exists on one side of the screen, this is a common failure for a panel.
I did notice in your original question you were asking if the LG model was the same as the Dell, well I have been unable to confirm this, but I am curious as to why you ask, do you have a LG that you have found for parts?
I am sorry to give you bad news, I know you were hoping for a better diagnosis than that but unfortunately these LCD panels fail a lot more often than we would like. Please let me know if there is more that I can do for you.
I you have any further questions, or would like more information, please do not hesitate to ask.
Also please never accept an answer until you are 100% satisfied, we have met all your needs and you feel that you can leave positive feedback. If we have not met all the criteria here please let me know and we will continue working on your problem.