..if you track "chipselect" in the sdfat you may see it has udergone an evolution:
..
uint8_t const SS_PIN = 53;
uint8_t const SD_CHIP_SELECT_PIN = SS_PIN;
bool init(uint8_t sckRateID = SPI_FULL_SPEED,
uint8_t chipSelectPin = SD_CHIP_SELECT_PIN);
chipSelectPin_ = chipSelectPin;
digitalWrite(chipSelectPin_, LOW);
.. so you have to touch a lot of files then..
P.