Command 'su' is not working in virtual console

[Marko Randjelovic <marko.mppa@gmail.com>]

I have very disturbing problem, so I hope someone will be in situation
to help me.

As I said in title, su is not working in virtual console for any
combination of from-to users. In gnome-terminal it is working. sudo is
also working.

When I type 'su', is't the same as I just typed RETURN without any
command, but exit status is 1.

Some time ago I had a problem when starting X applications with gksudo
that I solved by changing to --su-mode. But now it looks like working
again in sudo mode, but the problem I described appeared.

I tried to disable kdm, but didn't help.

I am running kernel 2.6.39 from unstable with some additional patches.

Any help is welcome.