The problems isn't just gaming or the Computer field, It' a bigger social problem.
Think about it for a second: why are some recent field held almost by exclusively by mens?
Take cars for exemple: This is a relatively new field, but it's held by mostly mens? Why? Because of the technical aspect of things. Women tend more to favor activity or feild that favors a social aspect.
I live on college campus and can witness this behavior around me:
Engineering: 70% guys
Medical School: 3 women
Nursing: 5 guys total
The computer is still a technical 'thingy' and, even though game are becoming more and more social (The Sims for exemple), it is still a men's world.
The fact that immaturity rules most FPS games doesn't help a bit. If I was a Women, I would probably NOT be a big gamer (maybe except for some RPG games).
I REALLY think we need more girls in computing and in gaming in general. They tend to bring out aspect of developpement left out by all-men teams (And they usually make great manager)
But what can we do?
(beside stopping the sexist jokes, the immatures comments and jugements,...)