cron-apt sends mails although there are no updates available

[Sven Schaefer]

cron-apt is executed every day at 4 o'clock. It's configured to send an email if there are updates available. Although the exact configuragtion is working under Debian, it does not with Ubuntu.

The daily mail stops with the message:
E: Failed to write temporary StateFile /var/lib/apt/extended_states.tmp

I've found a related bug for debian, which is already fixed: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=670222
The bug for debian should be fixed in aptitude 0.6.7-1

Regards,
Sven

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: cron-apt 0.9.0
ProcVersionSignature: Ubuntu 3.2.0-24.39-generic 3.2.16
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.0.1-0ubuntu8
Architecture: amd64
Date: Mon Jun 4 15:57:11 2012
InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
PackageArchitecture: all
SourcePackage: cron-apt
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.cron.apt.config: [modified]
mtime.conffile..etc.cron.apt.config: 2012-05-03T00:45:02.244664