Possible Duplicate:
How do I resolve unmet dependencies?
An error occurred, please run package manager from the right-click menu or apt-get in terminal to see what is wrong.
The error message was:
'unknown error:'<type 'exceptions.system Error '>' ('E:The package tty-mscorefonts-installer needs to be reinstalled, but I can't find an archive for it.' this usually means that your installed packages have unmet dependencies