[SOLVED] Precise Automatic Update -authentication not prompted?

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http://ubuntuforums.org – What have I missed? Precise, 2D Unity, Auto-login to a single admin account. Update Manager set to present all updates daily. Synaptic used for individual package management otherwise. Password always prompted for by that application at all operations. At the last couple of update presentations, Update Manager didn't prompt for admin password when okayed to install updates. From memory (I don't often manually invoke Update Manager) Update Manager *did* prompt for password when last used to update packages manually. Another machine running Lucid always prompts for auto update installs (Hardware)