Comment 23 for bug 498980

/etc/pam.d/common-pammount was a red herring for the bug submitter, who was not seeing a segfault.

For others who saw a segfault, having pam_mount called twice in the stack could account for this behavior, which I believe is what will happen if you've left references to /etc/pam.d/common-pammount in the config. Yes, you are supposed to remove these lines on upgrade, which is precisely what the NEWS file advises you to do.