ryreed how did you pinpoint it to the CSU ? Just so i know to check whilst its apart!
Put the steerer in a vice (padded/rubber face) with the fork horizontal. Put a bit of pressure on the lowers, or to be certain take the lowers off and apply pressure to the stanchions directly. I heard a clear ‘clicking’ sound coming from the yoke.
I sent my forks into SRAM via a dealer and SRAM said that whilst the forks were out of warranty they would replace the CSU and do a service for their standard service charge (approx £90). What I got back was a new fork with my damper inserted. New CSU, air spring, lowers (and obviously bushings/seals etc). well worth the £90 to my mind. They were OEM on a commencal I had from late 2009, I had reciepts and photos of them installed.
HTH
Edit: yep, as per Loco advice above.