Ok, here's the problem. Whenever I try to sign into the World of Minecraft Client, it gives the authentification error. I am sure that I am typing in everything correctly, and that it is the minecraft.net username and password,  and have tried deleting old versions of the client and redownloading the newest one multiple times. I've tried 3rd party fixes and fixes suggested on other topics on the forums, none of which worked. I have installed the client correctly and followed all of the steps on the Downloads page. I'm pretty sure it is just the account because it does this on other computers that I try too.                                                                                                                                                                                         This problem only started recently, and I can't figure out what is causing it.

I am running Window's Vista and have the latest Java update.

If you can help, thanks.