I am having problems with different SD cards in my project so to be sure, I made a simple test. I use seeedstudio Stalker (http://www.seeedstudio.com/depot/seeeduino-stalker-v2-p-727.html?cPath=80) and the basic example read write from SD.h library (http://arduino.cc/en/Tutorial/ReadWrite), I only change "SD.begin(4)" to "SD.begin(10)".
Now the problem is that if I use this SD card it works fine:
If I use another 1 Gb micro SD card that I bought in china, doesn´t work. The SD cards work fine in the PC, so I have no idea what's the problem. Both are formatted with FAT 32 and and default unit size.