I just installed Ubuntu 16.04 two days ago and the Ubuntu Software application works bad. Everytime I try to install any software, it stays installing forever without ending. Sometimes, after half an hour or so, I restart the computer and then the application is already installed, but sometimes it is not. For example, now I'm trying to install Shutter (in order to show you the error) and BleachBit but it just won't install. Other times I have to click twice on the "install" button but it asks me if I want to remove the software, because it was already installed... it's a mess.
The problems may occur for stale versions of software updater. Also with newer versions of
ubuntu releases they release regular patches. current stable LTS version is
16.04.1 so you can try updating your system
apt-get update apt-get upgrade
sudo prefix for super doer mode.
ubuntu community releases change summary for every patch release. You can get latest here