Authentication does not work with authenticate dialog

[Stefan]

Binary package hint: policykit-1-gnome

If a program is using the policykit authentication dialog (eg. Ubuntu Software Center, Hardware Drivers) the authentication does not work. It always returns to the Authentification windows, but with out a password prompt. From the .xsession-errors it is obvious that the process crashes. (the .xsession-errors file is attached.)
We use Ubuntu 10.04
The authentication is done over an ldaps/kerberos server

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: policykit-1-gnome 0.96-2ubuntu2
ProcVersionSignature: Ubuntu 2.6.32-24.39-generic 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic x86_64
NonfreeKernelModules: fglrx
Architecture: amd64
Date: Thu Aug 12 13:11:36 2010
ExecutablePath: /usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: policykit-1-gnome