Today for some reason printer HP Laserjet Ent 600 M601N Printer stopped working, it is giving the error code is 49.38.07 Error (4a04) on the display. It looks like the simple solution to fix this problem is to check what is in print queue — if you see there documents to be printed – highlight all if them and delete. Reboot printer and you should be good to go. The printer is back in business and error is gone. Now you can go trough firmware check and possible upgrade if exist.