Random Noise Problem on 2000 4.6L

I have a 2000 GT, 4.6L w/ 28K miles and it has recently developed an intermittent noise. It's a short whine that I believe is coming from the engine compartment. It started a few months ago and occurs only a couple times in 50 miles of driving. It's happened at a variety of speeds and even while the car is stopped and idling. I tried working the clutch when it starts to happen, but it has no effect (I originally thought it was a bearing). My latest guess after it happened again today is maybe an a/c, water pump bearing or maybe the serpentine belt.

Has anyone experienced this problem before? Any ideas?

Once again, noise problems are extremely hard to diagnose over the internet. Its one of things you've gotta hear and see to find.

How about radio interference? Happens a lot actually.