Could be a lot of things. How often per revolution ? Is it the same part of the pedal stroke that it clicks at ?
Chris Bass wrote:
i had this and one of the plastic cups that sit between the bearing and the axle had cracked, it started as a click and then developed into a longer noise a bit like you have described.
if you hold the pedals can you rock the cranks side to side? is there any play in the bottom bracket? try in a few different crank positions.