Whatever I write just ends up in the upper, left corner instead of in the password field. This started when I rebooted after Ubuntu performed an update today.

If I do Ctrl+Alt+F1, I see this:

[ 0.259413] platform MSFT0101:00: failed to claim resource 1 [ 0.259418] acpi MSFT0101:00: platform device creation failed: -16

(Ubuntu 16.10, I think)

Edit: One workaraound is to select an older kernel in the boot menu.