Bad tensioner pulley?, Alternator noise Options

[senick]

So I'm getting a noise from the alternator (pretty sure), and I haven't been able to solve it. My first thought was a loose belt, but checking the tension just by pressing down on it I think the tension is fine. It deflects maybe 1/2 inch if I really press hard. The alternator itself seems fine. I ran the engine with the battery disconnected, turned on the A/C at high, turned on the headlights and radio and gave it a good amount of throttle with no problems at all.
The noise is a squealing noise. It's not present when I first turn on the car, but starts up after the engine has warmed a bit. It gets louder with higher RPMs, and goes away for a second when shifting up. The car drives fine, but I'd really like to get this solved. The belts are only about a year old, and look fine.

[senick]

I can barely rotate it 45 degrees. Now I'm thinking the belt is too tight. I took it out on the highway yesterday, and after a while the noise stopped. After cooling down, it started a little bit again. So at least it's not the pulley, because why would the noise stop if it was.