The quickstart guide from Sparkfun instructed me to solder the headers onto the shield, but I am currently using the shield without the headers soldered on, to test it. How likely is it that this is the issue?
My microSD card is a 2GB card formated into FAT32.
Due SPI: SPI header (ICSP header on other Arduino boards) These pins support SPI communication using the SPI library. The SPI pins are broken out on the central 6-pin header, which is physically compatible with the Uno, Leonardo and Mega2560.
I reformatted the card to FAT (aka FAT16),