I still haven't figured out what is wrong. The only detail I didn't mention was that I updated the castle link software to the newest version.

Also, I cannot recalibrate anything because there is no communication between the receiver and ESC, even though the batteries are powering the servo. Furthermore, Castle's FAQ says that I should mess around with transmitter settings, which I have, but specifically to set the endpoints to between 100 and 120%, which I also have done. I'm running out of patience and ideas on what went wrong in the 20 minutes I stopped running it. I will try to revert to older software, but I don't know if I can do that off the top of my head.