I'm still having trouble with the uFat library
I've used the Roland library and is quite happy with it. There are some issues with compiling (as the library was not made for Arduino), but it is fairly straight forward to fix.
To me it seems as if you have hardware issues. One thing to consider is your 3V3 power supply. Using a voltage divider to power logic circuitry is generally no good. The issue here is that voltage will jump up and down as current through the divider changes. You will be better off using the Arduino 3V3 output as it is regulated (50mA is plenty).