I think there may be an issue with resizing atm.
I've repeated this multiple times today with the same result.
Create a new VM (Japan East / West) login OK. (2012 DC R2)
Downsize it.
Wait for it to restart. > Can no longer login.
Shut it down, restart it, resize it back nothing will bring it back.
As I mentioned I've repeated this multiple times. Seems like a pretty frustrating way to lose a VM. Anyone in Azure aware of this issue?