Well, I figured out the problem. As it turns out, since I'm hosted with GoDaddy, there was a problem with writing session data to a directory that either didn't exist, or was denied permission to write. So for anyone else with this horribly misleading error, here was the solution:
PHP Code:
session_save_path('/home/content/blah/blah/html/temp');
I inserted this line into class_session.php, just before session_start(), replacing that path with the absolute file path for my host. I then made a file called "temp" and made it writable, so bazinga. It works now, I can log in to mysidia.
