(there are a scattering of resistors on the module but they don't appear to be in series with those digital lines)
Whatever the case, I just tried to drop in five 10k resistors on the spi (and reset) lines, and the module stopped working. Removed the resistors and it's working again. *shrug* Either I bruised it and it needs 5v on the lines now, (I've done that a time or two in the past) or there's something on the module I'm not seeing. The module is marked "RFID-RC522"