Okay, this is most likely a one-time thing, but I just got the game to load again.
Here are ALL the relevant details
Firmware: 3.2U
cIOS: rev7
Loader: NeoGamma R4 RC4
Loader settings: All default
Controller: Nunchuk attached to Wii Remote, Wavebird (wireless Gamecube controller) connected and turned on, and Ghostbusters disc inserted all before turning on Wii
After launching NeoGamma R4 RC4 through the Homebrew Channel, I laid the Remote down (not touching it at all) and used the Wavebird to navigate the NeoGamma menu. I didn't change any options, but pressed A on the Wavebird to select Launch from DVD in NeoGamma.
Chances are good this is just another random success. I'll test again here in a few and post again.
EDIT: Yep, looks like this was a random success, too.
The game locked up at the Wii Remote safety screen on the second and third attempts with the same settings and procedure.