I can only guess, since I don't know the
history of your system, the passwords
you have chosen, or how many other accounts
are in question here.
1) If you have # or @ characters in your
password, funny things will happen because
these are sometimes interpreted as line
editing characters. Different programs
interpret them in different ways. (This
goes back to the days when system consoles
tended to be hardcopy devices. A few
remnants of that persist in the code.)
2) If you have converted to/from trusted
mode AND have passwords longer than 8
characters, behavior can be unexpected.
If this is the case, try using only the
first 8 characters of the password. This
is a side effect of some capacity limits in
how passwords are internally stored and the
inability to convert from one form to another
in all cases without losing some data. In
standard mode, any characters after 8 don't
actually get stored in your passwd entry
and get ignored on input, so it APPEARS
that you have a long password even though
any characters after the first 8 are silently
ignored. This is standard UNIX behavior,
but not widely known.
I have no way of knowing whether something
like a site policy requires superusers to
have long passwords, etc. That could be
one reason why it only happens to superusers.
