Maybe there is some innate difference, but with a wide variety of societal factors in play I think we're probably on safer ground eliminating them from the equation before we declare that women are somehow less likely to have technical aptitude by nature.

A lot of people have said that our brains are wired differently. I highly recommend Delusions of Gender by Cordelia Fine, it's looking into exactly those claims:

http://www.cordeliafine.com/delusions_of_gender.html

Other technical fields have a higher male/female ratio, so neurological gender differences doesn't seem like a promising hypothesis.

The only technical fields I can think of with significantly higher ratios are either a) softer (biology), or b) have a teaching track which attracts women (math teacher).

When I was in grad school, the math major had lots of women. The vast majority were education minors. The undergrads taking grad courses (note: every serious math major does this) were mostly men.