eNTy
Legend
Silver Level
quicktime turns green
...may help for QT. I don't think .mov files are supposed to open in anything else. Maybe vlc plays them now, who knows. It sounds like it's a codec problem though, or maybe your qt version isn't up to date?
AFAIK VLC plays pretty much anything except maybe a couple of rarely used file types. What I do get sometimes is when I open something in VLC i get the green screen thing too (only mine is beige for some reason but I used to have green too) but if I close VLC and start the same movie up again it's fine.