This happened to my game after having it opened for a week, and my computer on for 3 weeks.

https://www.youtube.com/watch?v=WaLU0g85Hbs

It was fine again after a computer restart =D

I've seen this too, if I leave LFS on for a long time and thrash my computer with high-res photoshop or video encoding etc. It goes with just an LFS restart though, I've not needed a computer restart to clear it.