Why am I asked for the "password for root" when upgrading packages?

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http://askubuntu.com – I have a fresh install of Ubuntu 12.04. I installed with one user account, then added a second user account using the GUI dialog box method, making myself an Administrator type. I now use the second user account. When using update manager and it needs to add or remove packages, it asks me for the "password for root" rather than my own password. I've installed and used a lot of Ubuntu systems and never been asked for the root password before. I know how to set a root password so I can work around this situation. sudo works fine and I'm very comfortable on the command line, so I can do ever (HowTos)