I've had a solid film form on several of my beers. If disturbed it breaks up into a bunch of small little floaty film islands. I know several people on the site have mentioned having it at least once, and the consensus seems to be that it doesn't give off-flavors. It is definitely some kind of infection and it happened in the same fermenting bucket each time before I gave it a thorough bleaching. Although it doesn't sour a beer, I've noticed it does give it an odd, subtle, almost fruity flavor that now I can recognize what it's from, I detest. The beer is still drinkable, but those batches that had that infection are sitting in the beer closet, collecting dust.