For me, a crosswind seems to blow the bottom of the bike out from underneath me.
If I know I'm jumping with a crosswind, I try to turn into it a little just before takeoff. That doesn't really make any sense to me because it implies that I'm leaning the bike in a direction I already know it's going to go (badly) when the wind hits me, but it seems to work. I hesitate to even mention it, because it doesn't seem to make sense, but it seems to work for me.
One thing I do know that helps is to grip the bike with your legs/knees on takeoff and all the while in the air. That seems to ensure that you and the bike move as a single mass rather than two separate objects merely flying in close proximity. :)