Well I dont really know whats happening, but just to share :

I had this mmc ( 32 gd Sandisk class 10). It works like copy files and stuff but it simply wont adjust a swap on itself. It did everything right except swap. For swap, it used to give those I/O errors adn device used to reboot after 20-30mb of write. Formatted it thousand times but to no avail..

Maybe try a new sd card. Since I/O error is from PC to card too, maybe issue is with card only.