I tried to install Synaptic Package Manager but I get the following error message:
Package dependencies cannot be resolved.
This 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.
On the terminal type in the following commands (one line at a time) >>
Just go here and install offline way if this helps. Synaptic packages for 12.04
If this is happening then you either have a package version that is lower than the required dependency version or one of your packages is broken.
You can try fixing the packages by running your update manager and checking for updates and installing them.