That sexism impacted Clinton's campaign, I have no doubt. Did she lose a close election because of sexism? I don't know. But I do know that it will never happen again as long as women are willing to stand up and make sure that it is just a one-time bad experience.
No, Hillary did not lose because she's a woman. And Obama did not win because he's black. I'm sure that residual sexism and racism (including the racism displayed by Ferraro herself, which got her kicked out of Hillary's campaign) played some role in how this primary election played out, but in the end I think the nation came to realize that Obama is simply a better campaigner and a better candidate. Why the Clinton supporters continue to deny this possibility so stubbornly is beyond me.