For some reason, whenever I start up the computer and when I restart, the volume automatically lowers to about the one-quarter mark. I have the sound icon at the top right corner of the screen on the menu bar. I'm sure it hits the same point every time. Strange.
Possible suspects: Perian, Flash, Logitech mouse control center, AudioHijack plug-in.
I guess that did it, but I'm embarrassed to say I think my sound settings were at that one-quarter default.
On a related note, I've had this problem before, I want the startup chime to ring only through the headphones. I have the headphones plugged in all the time.