Can't log into existing account with Steam on new Ubuntu install.

I'm playing around with Linux Ubuntu and have installed the Steam Client, but it keeps telling me my password is wrong when I try to log in.
I know I've got the right password, because I'm here writing this... ;)

This is a dual boot system with Windows 7 and Ubuntu LTS 14.04

Is there something I don't know. IE do I have to log out of the Windows 7 side first before logging into Steam via a different OS?

Or is Steam on Linux just that bugged?

Can't log into existing account with Steam on new Ubuntu install.