I uploaded a video with the noise:
"http://www.youtube.com/watch?v=gk7dwgjbcDo"]YouTube - Syil Super X3 Spindle Noise
There is no play in the spindle itself, it is pretty solid. There is play between the pulley and the spindle as you turn it left-right, but that is all. The noise is not there if I let the motor run by itself (no belt) or if I turn the spindle by hand.
Any ideas on what to do next?