[Brian]

You know, I'm honestly not sure what would cause that behavior - I often leave my mac idle for hours at a time, and I've never had Mail ask for permission to unlock it.

<wanders off to do some googling...>

Sadly, didn't turn up much. Hmmm. Do you have syncing enabled? The only thing I can think of is that the keychain isn't unlocking as expected, so every time we try to do a sync, you have to re-authenticate. I guess another possibility would be that the keychain is unlocking, but then something re-locks it automatically a short time later.

Is there any other software on the machine that could be re-locking the keychain? Does anything appear in the console log when this happens?