The following hints were taken from
http://wiki.ubuntuusers.de/aptitude
http://wiki.ubuntuusers.de/Paketverwaltung/Problembehebung
http://wiki.ubuntuusers.de/apt/apt-get
The installation was interupted unpredictable:sudo dpkg --configure -a
(Enter, Password Enter)
“Broken” packages are reported, repare:sudo apt-get install -f
(Enter, Password Enter)
Update without upgrading to a new ubuntu releasesudo apt-get install dist-upgrade
(Enter, Password Enter)
Repare “broken” packages or to delete the cache of the program list:sudo apt-get clean
(Enter, Password Enter)
To reload the program list againsudo aptitude -f install
(Enter, Password Enter)
Package administration is not usable anymore
Should the package administration become unusable during an upgrade or dist-upgrade you can use:sudo aptitude -f install
(Enter, Password Enter)
After an update of the existing installation:sudo aptitude safe-upgrade -f
(Enter, Password Enter)
After running a version upgrade to a new ubuntu version:sudo aptitude full-upgrade -f
(Enter, Password Enter)
After these statements you should always runsudo dpkg --configure -a
(Enter, Password Enter)