Didn't want to clog up the thread with off-topic stuff, so I thought I'd come here.
I don't really know why the cached data isn't working for you, but I'd still have to suggest just allowing Firefox to save the passwords for you. Remember, even if you enable this feature in Firefox, you'll still be prompted as to whether or not you want the browser to remember the password, so if there are websites where you don't really find that necessary, you can just select no.