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.
details:
The following packages have unmet dependencies:
flashplugin-installer:
how can I fix this?
To install the flashplugin package on Ubuntu, open up the Ubuntu Software Center, and search for "flash" (without the quotes). After you install it, restart your web browser(s), and Flash should be working!
Try using aptitude:
sudo aptitude install flashplugin-installer
If you don't have aptitude installed on your machine sudo apt-get install aptitude.
Hope this helps.
