Text changing darkness in word

[Eagle156]

I have to work on a 5 page essay (aaargh!!!) and I have a very weird problem. When I'm typing all of a sudden some part of a sentence (usually around 10 words) becomes darker. It looks like it's bold, so you can understand that this is very annoying and I don't know how it will actually look when I print it out. I can get the darkness to disappear if I scroll up or down so you can't see the text that was dark, and it will look normal again when you scroll back up. The weird thing is that the dark text will stay there no matter how much I scroll up or down (while still having it on the screen) so I don't think it's burn in or something. I THINK it's my monitor since I never had this with the old CRT, but I'm not really sure. It's a Samsung 940b and it works fine for pretty much everything else. Or maybe I'm dumb and it's some kind of uber secret bold feature of Word.