2002 Mitsubishi Eclipse Squealing belt

I have a 2002 Mitsubishi Eclipse. Recently I replaced the Serpentine belt because it was squealing and was worn. The squealing returned shortly. I lubricated the belt and the squealing continues. My husband thinks it may be a bearing. The squealing mainly happens when the engine is stressed, such as turning on the a/c or turning the wheel sharply at a stop. If it's a bearing, how do you figure out which one? I think it's the A/C compressor because the A/C isn't working.