Erm, how were you able to run
passwd if you could not login?
I'm not sure how Mandriva handles things, but it's possible that either or both of those accounts you mentioned are locked. Even setting password might not unlock the account, but root must use
passwd with the appropriate option; check out
to check out which option is the
unlock option, and pass it as a parameter to passwd along with the account name, if you can log in and gain root privileges with
su or something. If you can't, then boot into single user mode (add
single to the boot line) where you are automatically logged in as root, and set the passwords and make sure the accounts are not locked. And after this remember to set a bootloader password, so that nobody else does the same trick
