From Mailvox: Women in Science:
I have seen them work well in support roles, but not as designers. Best I can figure is women are more balanced in their approach to life, that is why the do better in school, but get blown by in most real world situation. Fact is the folks that succeed in any field are not exactly balanced, they eat, sleep, live and die by their profession. Second to these folks (not one myself) are people that do the field as a means to an end, but they are driven in some vocation that the engineering field pays for. It is a means to an end and they are still driven folks and do not want to waste their time at work.
None of the women cared enough to be thinking about the problems at lunch, when they drove in or on their time off. None of the women want to put in the hours when there is stress situation, which is when the best engineers show what they are made of.