I've had elementary installed for six weeks or so, no problems. When I went to log in today I decrypted the drive as normal then got the log in screen for my only user account. I logged in and caught a few buttons which rotated the screen by 180. Having tried various key combinations and an online search to no avail I restarted, decrypted the drive and the screen was the correct way up. Note that during the first login I was charging a device by USB. I unplugged it prior to restart. Now I can't log in, I input my password and the login dialogue shakes to indicate its incorrect. I tried several alternate key maps for the same password and still no joy. Pressing control alt f1 gives me command line which also does not let me log in. When I type the password into the terminal I can see it is correct. I have tried restarting, power off, battery removal. As far as I can tell I am inputting the password correctly. Any help would be much appreciated.