<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Cloud Lounger:
(Note that C zeroed out but there are still 19 open?!) I will report back on the outcome after the flight.</font>
This is normal. If a flight is still overbooked close to departure date, they will close C class out and get ready to use the J cabin for upgrades. (Sometimes they will also shift some J capacity down into Economy class if J is empty and Y is full.) Seems like it's the former case for this flight.
Good luck.