I just now remembered because I had to do it... But I _knew_ there was a way to get into a Debian box from grub.. Instead of booting with 'single' or '-s' which asks for a password, boot with this:
I was unable to change my password this time (I have brain farts often) because I could not remember how to remount / as writable... But once its up, just remount the root partition as writable and then run 'passwd' to change the password.