Ok, I hav'nt worked too much with OSX, but I more or less live on the command line.
first off, I assume you already know that when type in the password it will not show your cursor, show it move or anything else.
try useing su to swich to another normal user. I recall there being something a little weird about osX trying to keep people out of the root account.
so try using your normal gui tools to make an accout for say user bob, with a password your sure of then from your normal account try
bash$ su bob
Password:
you know. I just looked it up.. apparently they don't let people log in as root, you need to use sudo. try
bash$ sudo bash
that should launch a shell that has root accsess in the window your working in.
oh you might also want to look at
bash$ which sudo
hope some of that helps
[EDIT]
this is probably better advice than I am giveing.
http://www.osxzone.com/static/hacks.html