I dunno what happened, but I suggest that the first thing you do after reinstalling Lion is check Software Update (wherever it lives...System Prefs or App Store) and make sure it's not set to "auto".
And just to clarify, you confused me by mentioning Keychain Access; it doesn't have anything to do with what you experienced.
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In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire
