Application installation error on updated Mac mini of Mac OS X Lion
Your Mac mini Mac OS X Lion is not concern with the pop-up error messages in installing an application, it's the App Store is concern with it. Contact the App Store and tell them your concern about installing the application, there was an error occurred during installation that caused incomplete request.
I have a solution to resolve this matter. You have to install “OS X Lion Update” from the following link.
The 10.7.4 update reinstalls the App Store for you which may help. You can do this even though you are already running v10.7.4.
Restart your Mac OS after the combo is installed. The problem will be solve hopefully.