There's a bug in PR1.2 (fixed already - awaiting the next public release) that means every first letter in the textboxes on the login screen is always a capital, including the password box (which you can't see what you've written in.) I reported some similar issues in PR1.1 in the TweeGo bug tracker. Type the first letter of your password twice, and then delete the first letter of your password - that should work. (Yes, I know that's a bit bonkers.) Maybe the TweeGo authors can set something on the textbox to turn off auto-complete and stop it behaving like that?