I'm with Paul on this one. However, the older style solid couplers are prone to wear also, and can cause blower chatter too.
The likelihood is that your snout seal failed, resulting in a loss of lube in the blower. You should be able to tell if that is the case by grimy black deposits under the snout near the pulley, or a wet mark on the hood blanket (if your car still has one installed) right inline with the pulley and belt. Depending on how long the car has been run with low fluid in the snout, you're best to have the snout rebuilt at least, including a new snout seal, a new coupler, and some fresh blower fluid.
The solid couplers can be obtained from ebay. Just do a search for 'M90' or 'Eaton M90'. I believe the couplers are the same for our blowers as they are for the GM Eaton blowers (M90, M62), so you may find some GTP guys selling them. If you do a search here in these forums, you should be able to find listings of part numbers for the seal and the bearings in the snout. A little more digging, and you may find Dr. Fred's instructions on how to rebuild the snout of your blower.
In the event you're not comfortable rebuilding the snout yourself, you can always send it off to ESM or Magnum Power for a rebuild and/or porting. I believe that both of these companies offer a one year warranty on their blower rebuilds.
Best regards,
Sean