This is a follow-on from a related question http://forum.arduino.cc/index.php?topic=385727.0.
I have a project that writes to an SD card. I believe I've eliminated software problems (see original postings) so I think it's probably something to do with one of the 4 pins that SPI use.
My question is this, can I deduce anything from the fact that the I can still create files, but I can't add data to them? So each time I run a test I end up with a zero-byte file (of the correct name) but with no data in it.