Samba domain member cannot unlock screen

I have several boxes at home, with a mixture of openSUSE and Windows, and am trying to create a domain with them. One box running openSUSE with samba acts as server, providing shares, domain master and domain logon functions. This is working, and I can join another openSUSE box to the domain, and log in as a domain member using winbind.

There is one problem I cannot find a solution for. On the client (openSUSE 12.1 with KDE), I can lock the screen in the usual way, and then get the “The session is locked” dialog. When I enter the password, the response I get is “Unlocking Failed”.

Possibly useful extra information:

  • I have seen this with both openSUSE 11.4 and 12.1, on two different machines.
  • Lock and unlock works in Gnome; the problem is only in kde.
  • I cannot find anything in the logs.
  • Entering the wrong password gives a “Wrong Password” message, so I am sure the password is correct.
  • Lock and unlock works for a local user on the same machine.

I suspect that the problem lies either in permissions or integration of kdm with pam, but have nothing to support this. Searching has produced nothing useful.

My questions, and I would appreciate answers to any of them, are:

  • Has anyone else seen this?
  • Is it a known problem?
  • Does anyone have a solution?
  • What should I try next?