Since Update to 1.0.0 MC have a lot of bugs. One of it is that Minecraft says everytime you try to login(minecraft.net): Oops, unknown username or password.
I searched for this bug in google and I am not the only one. Since 11-21-11 Much people are having this problem. If I try to login with launcher same. It can't login and don't download something. I deleted my .minecraft folder+minecraft.exe+Used CCleaner for cleaning cookies and so on.