I have about 98K on my Xfire and it started squeaking recently. Turns out that it was one of the pulleys. The dealership told me that it was the alternator (They used a stethoscope to track it down). So I changed that out. Still squeaked. Argh!

Then I took it back in to them and they figured out that it was the tension pulley and they replaced it free since I was out the money on my alternator.

Check those out and let us know what you find.