Wheel bearings is the problem, I just had the same issue with my XFire. It would make a loud squeak, but then all of a sudden quit. So, I just let it go, and then about 500 miles later I found out my wheel was about to fall off. So, to make a long story short I had to replace both bearings including the spindle due to the bearings welding themselves. Chrysler said that the bearings were made very cheap, so XFire owners beware.