This has been happening to my tv (Samsung LN32B460) for sometime, but now it seems to be getting worse! This green light occurs on all the inputs (I only have hdmi connected devices), and is sometimes even visible over color pictures though black is when its most apparent.
I took it to Best Buy within the 1 yr warranty and Samsung said there was no problem with the tv. The tv is still fairly new. I think I bought it in May 2009, and I have probably only watched about 100 hours of tv/bluray. It's a bedroom tv so it doesn't get much usage.
Is this something that can be fixed? Is it even economically feasible to fix? I'd hate to have to buy another tv, but it's really annoying!
Check the link below. It has pics of problems with LCDs and causes. I don't see the exact thing you show but a few are similar and point to a bad panel? Check it out and maybe one of the pics will be close enuf for a possible solution: