Macbook Pro freezes after I enter my password

ONE SOLUTION: if you've a spare OSX hard drive, re-fit it, and connect the SSD via SATA_USB cable. Boot holding alt, and select the SSD. It should be able to logon without issue. Next, shut the machine down, take out the old hard drive and refit the new, power her up, and the problem, for me at least, was solved.