What's making this sound on my Mac? (DeliveryCompleted.aiff) Several times a day, my laptop plays this unknown sound. There's no visual cue that goes along with it and I have no idea what it means.

I assume it wants my attention for something, but without knowing what, I'm stuck. On the other hand, if it's something I don't really need to know, then I want to make it stop.

I managed to track down a file on my system that has the sound...  

afplay "/Applications/Xcode.app/Contents/Applications/Application Loader.app/Contents/Resources/DeliveryCompleted.aiff"


Any ideas as to what that sound is supposed to mean?
Turns out it was Adium's way of telling me a new contact had signed on. I disabled the sound in Adium's preference and it's gone away.