Don't know if this will help (I use KDE, not LXDE), but it may be worth a try. Boot to safe mode. This should bypass the need to enter a password. Type PCC <enter>. Select keyboard. Choose OK. Select US international. OK. exit. Reboot. Enter password at login. Change your password to something simple. Now choose your actual keyboard. After your next reboot, change your password to something more secure that is found on your keyboard layout.
If this works, you've averted a major headache. If not, you've only lost a very few minutes.