Why Girls May Be Misdiagnosed
I ran across this article on girls and Asperger Syndrome last year, but it's still a pretty good one.
The "gender gap" in autism is not actually unique to autism. Girls are diagnosed with learning disabilities less often than boys across the board, and those who are diagnosed tend to be caught earlier and have more severe symptoms. That could indicate that those with milder symptoms are simply missed. Maybe it's because of social pressure from teachers or parents to avoid a "label." Maybe they're just better at fitting in with special interests that are less odd and greater social skills.