i fear we may have overlooked the basics or looked at incorrect bearing
read this site has good info on diagnosis..
HowStuffWorks "Common Problems and Other Types of Clutches"
read all of it before moving forward but due to noise goes away when clutch depressed or revs increased
i would either go with springs on clutch plate loose OR throw out bearing
remember the throwout bearing is under more stress when engine running then when is spun in your hand
another VERY COMMON getrag problem is that the throwout bearing doesnt sit evenly on the shaft properly
or that its noisy spinning on the inner race INSTEAD of spinning on the bearings in the middle
the cheapo fix for this is to grases LIGHTLY the input shaft where the bearing fits onto it
but either way i would be replacing the bearing AT LEAST if not the clutch plate itself aswell (buy a kit)
and also LIGHTLY greasing the input shaft where the throwout bearing sits on installation..
hope this helps man!~