Ah, following the lead in the log paid off. I had to add the statement XSendFilePath /panfs/galaxy_data to /etc/httpd/conf/httpd.conf. Apparently ever since I had moved the dataset directory to /panfs/galaxy_data by setting the "file_path" variable in universe_wsgi.ini I have not attempted to view a dataset, and so I didn't even notice that the functionality broke when I moved it at first. I just needed to point XSendFilePath to the new directory and it worked. I hope this helps someone else if they encounter the same problem.
Cheers,
Josh