After returning my first treo for the infamous buzzing heard only by the other party, and the second for arriving SIM-locked, I have a third unit with a brand-new problem.

This one buzzes the way the first one did, except that I can hear it too. In addition, if the device is anywhere near my desktop PC, the PCs speakers emit the most horrible shrieking noise whenever a call or an SMS comes in. With the previous two units, this was a brief, gentle hum.

I don't think I've read any posts involving a hum that both parties could hear, but I did read some that associated the noise with use of the 850MHz band. Is it possible that the second unit, with AT&T customization (and unfortunately SIM-locking) contained logic that somehow reduced 850MHz interference?