I've found that the problem with most nice guys that have confidence is that they treat women as equals (tis was me a looonnnggg time ago). Women are not equals. Women want to serve a man and make him happy. Women need to be told what to do...it makes them feel secure and allows them to avoid responsibility for their actions.
Reminds me of a good line from As Good as It Gets. The chick in the publisher's office asks Jack how he writes women so well, and he responds "I imagine a man and strip away reason and accountability."