Apport is a debugging tool that automatically generates crash reports. In the final Ubuntu 12.04 release, Apport seems to be enabled by default (unlike in the previous Ubuntu versions) and at least on my system, I keep getting "Sorry, Ubuntu 12.04 has experienced an internal error" popups, which can't be reported, a few times a day (Apport bug already reported).
To get rid of these annoying Apport popups, you can disable Apport, especially since most of the time there are no visible errors / crashes anyway. Sure, this won't solve the actual errors, but at least you won't get those frequent Apport "internal system error" dialogs anymore.
To disable Apport, you need to edit "/etc/default/apport" with a text editor such as Gedit (as root):
and change "enabled" from "1" to "0", then save the file.
gksu gedit /etc/default/apport
After completing the steps above, Apport won't be started at boot anymore, but let's stop the running Apport process too, so you don't have to wait until you restart your computer:
sudo service apport stop
You can always re-enable it later on if you want, by changing "enabled" from "0" back to "1", or you can enable Apport temporarily, using the following command:
sudo service apport start force_start=1