There was a journal paper about a year ago by Sapna Cheryan called Ambient Belonging: How Stereotypical Cues Impact Gender Participation in Computer Science that you can read here:

http://www.comp.dit.ie/dgordon/Courses/ILT/ILT0010/Ambientbe...

The dumbed-down version is here:

http://www.wired.com/wiredscience/2009/12/star-trek-keeps-wo...

In short, it appears that CS has a serious grassroots marketing problem.