You may also want to know that you can use
dpkg --audit to see what the actual problem is.
If the output is something like:
The following packages are in a mess due to serious problems during installation.
They must be reinstalled for them (and any packages that depend on them)
to function properly:
gcdemu A GNOME panel applet to control CDEmu daemon
The following packages have been unpacked but not yet configured.
They must be configured using dpkg --configure or the configure
menu option in dselect for them to work:
cdemu-daemon CDEmu daemon
cdemu-client A simple command-line client to control CDEmu daemon
The following packages are only half configured, probably due to problems
configuring them the first time. The configuration should be retried using
dpkg --configure <package> or the configure menu option in dselect:
transmission-daemon lightweight BitTorrent client (daemon)
vhba-dkms VHBA virtual host bus adapter module
You could run the command:
dpkg --configure <packagename>
dpkg --configure cdemu-daemon
In order to
Reconfigure an unpacked package.
If -a or --pending is given instead of package, all unpacked but unconfigured
packages are configured.
Furthermore you could use:
sudo apt-get -f install
sudo apt-get --reinstall install gcdemu
To fix the packages that are in a mess.
Examples from here: http://ubuntuforums.org/archive/index.php/t-1502826.html