I had the same problem, it looks like pexec is no more working on recent Ubuntu version. It was generating a lot of crash windows at startup.
A quick and dirty fix (no more errors at least): # sudo mv /usr/bin/pkexec /usr/bin/pkexec.old # sudo ln -s /usr/bin/sudo /usr/bin/pkexec Sincerely Technical Details: ProblemType: Crash Architecture: amd64 CrashCounter: 1 Date: Sat Nov 9 14:35:29 2013 DistroRelease: Ubuntu 13.10 ExecutablePath: /usr/bin/pkexec ExecutableTimestamp: 1379527177 ProcCmdline: pkexec /usr/lib/update-notifier/package-system-locked ProcCwd: /home/mystercoco ProcEnviron: TERM=xterm SHELL=/bin/bash PATH=(custom, user) LANG=fr_FR.UTF-8 LANGUAGE=fr_FR XDG_RUNTIME_DIR=<set> ** Changed in: policykit (Ubuntu) Status: Invalid => Fix Committed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/875402 Title: pkexec fails with ERROR:pkexec.c:138:pam_conversation_function: code should not be reached To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/policykit/+bug/875402/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs