Display Problem on MacBook Pro 13-In: red blotch when screen is dark/black
I've been having a really weird problem: a red blotch near the center of my screen, visible if the screen is black, or dark background in video playback. It's about an inch off center (right) and it look like a "T" made by a paint brush stroke. When it first appeared (in the same spot to the left of center), Apple replaced the display (in the last year of Apple Care), and it disappeared. It reappeared 4 weeks later as clear lines (in the same spot). They replaced the display again, and it disappeared once again. It happened a third time 4 months after that, and they replaced the logic board as well as the display; again, "fixed." Here's the weirdest part: because, after all this, the computer would not charge, they threw up their hands and gave me a brand new MacBook Pro. That was a month ago, and last night, there was the red blotch again (except now, again, just to the right of center).
I can't find anything like this (online) happening to anyone else, and so far Apple hasn't determined what they think the problem is. I sort of feel now the problem must lie with me. But what could I be doing? I haven't dropped it; I'm just using it for email and reading online.
Anyone have any idea what this might be? Thank you very much in advance for any suggestions.
MacBook Pro, Mac OS X (10.7.4)