January 6, 2010 4:11:05 PM EST
I'm not a PLO player, that being said:
1. Fold preflop. 499K single suited is an awful hand to be calling raises out of position with (even with that many folks coming along preflop)
2. Don't fold the flop, you should be checkraising there. Yes, it sucks that you could be up against a combo straight/flush draw on that board. But since you have a K in your own hand, the chances you're up against the two case Kings for top set against your middle set are pretty slim. So I would assume at that point my set of 9's is the best hand.
You could wait until the turn if you want to try and see if you can dodge the straight or flush card first before committing your stack. But the problem here is there's a half-pot bet on the flop and then a minraise from the button, so I'd be less inclined to let either of them draw for free.