Actually I don't have an answer, except it happens to me when I leave my cursor near mp3 id tag's in the search window it will suddenly do this. I don't think it's anything to panic about. I had considered posting about this myself some time back but forgot all about doing it.

Actually I just checked it out & it's the same thing when I check out my incomplete folder. It's the mp3 id tag info's that seems to send LW crazy. Luckily you're in OSX & not OS9 or earlier where it might affect other things. In osx I think we're pretty safe with its ram management. But annoying, that flashing is/can be. I just try to be careful not to leave my cursor hovering over mp3's for too long or without direction/thought.