I don't see yet here in the forum a dedicated topic for the new Intel Galileo motherboard in the Products board. Thus, I would recommend you to post this same question about your issue with SD datalog of ADC values to the Intel support community. https://communities.intel.com/community/makers
There are lots of Intel Makers and external Makers (Arduino/Atmel) keeping an eye on the Galileo support forum, and you might find answers quicker there than waiting here. Just a thought. Regards!