package samba4 4.0.0~alpha18.dfsg1-4ubuntu2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 126

[Pi-Rat]

Ubuntu 12.04 LTS
samba4:
  Installed: 4.0.0~alpha18.dfsg1-4ubuntu2
  Candidate: 4.0.0~alpha18.dfsg1-4ubuntu2
  Version table:
 *** 4.0.0~alpha18.dfsg1-4ubuntu2 0
        500 http://mirror.cs.umn.edu/ubuntu/ precise/universe i386 Packages
        100 /var/lib/dpkg/status

I was actually trying to intall gnome-session-fallback from the terminal, as I am stuck in the "User Defined Session" mode, and this error code was displayed and the package I was trying to install was aborted. Only just upgraded to 12.04 2 hours ago.

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: samba4 4.0.0~alpha18.dfsg1-4ubuntu2
ProcVersionSignature: Ubuntu 3.2.0-24.39-generic 3.2.16
Uname: Linux 3.2.0-24-generic i686
ApportVersion: 2.0.1-0ubuntu8
Architecture: i386
Date: Tue Jun 12 00:54:15 2012
ErrorMessage: subprocess installed post-installation script returned error exit status 126
InstallationMedia: Ubuntu-Netbook 10.04 "Lucid Lynx" - Release i386 (20100429.4)
SourcePackage: samba4
Title: package samba4 4.0.0~alpha18.dfsg1-4ubuntu2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 126
UpgradeStatus: Upgraded to precise on 2012-06-12 (0 days ago)