hey are a common source of problems.
Furthermore run the following command in a Terminal: apt-get install -fzCThe selected file may not be a GPG key file or it might be corrupt.zRThe selected key couldn't be removed. Check that you provided a valid fingerprint.z“Check if you are currently running another software management tool, e.g. Synaptic or aptitude. Only one tool is allowed to make changes at a time.ztThis is a serious problem. Try again later. If this problem appears again, please report an error to the developers.zWCheck the spelling of the package name, and that the appropriate repository is enabled.z#There isn't any need for an update.z(There isn't any need for an installationz#There isn't any need for a removal.zLYou requested to remove a package which is an essential part of your system.zQThe connection to the daemon was lost. Most likely the background daemon crashed.z9The installation or removal of a software package failed.z'The requested feature is not supported.z˘There seems to be a programming error in aptdaemon, the software that allows you to install/remove software and to perform other package management related tasks.záThis error could be caused by required additional software packages which are missing or not installable. Furthermore there could be a conflict between software packages which are not allowed to be installed at the same time.z?This requires installing packages from unauthenticated sources.zŐThe installation could have failed because of an error in the corresponding software package or it was cancelled in an unfriendly way. You have to repair this before you can install or remove any further software.zKPlease copy the file to your local computer and check the file permissions.zďThe installation of a package which violates the quality standards isn't allowed. This could cause serious problems on your computer. Please contact the person or organisation who provided this package file and include the details beneath.z˘The downloaded license key which is required to run this piece of software is not valid or could not be installed correctly.
See the details for more information.z3All available upgrades have already been installed.z}The license key which allows you to use this piece of software could not be downloaded. Please check your network connection.z>You don't have the required privileges to perform this action.zńYou either provided a wrong password or cancelled the authorization.
Furthermore there could also be a technical reason for this error if you haven't seen a password dialog: your desktop environment doesn't provide a PolicyKit session agent.z Failed to download package filesz)Failed to download repository informationz'Package dependencies cannot be resolvedz