Problem with microSD SPI mode in AVR

I'm trying to read a microSD block. But I don't know why it doesn't work.

I do:

CS_UP;
for(uint8_t i = 0; i <14; i++){ /* Send 74+ clocks */
    spi_tranceiver(0xff);
}
_delay_ms(1); /* Wait 1 ms */

//CS_UP;

/* Initizalize microSD */
put_string("Go to idle state\n");
while (Reset_Card() != 0x01) // Go to idle state
    ;

put_string("Send IF COND\n");
while (Send_CMD8() != 0x01) // SEND IF COND
    ;

put_string("Send ACMD41 and CMD55\n");
for (int i = 0; i<100; i++)
    while (Send_CMD55() && Send_ACMD41())
        ;

setBlockLen(); // Set block read in 512 bytes
CS_DOWN;
put_string("\nConfigure finished correctly\n");

And then I just call:

readSingleBlock(0x00, &buf)

readSingleBlock is defined as follows:

uint8_t readSingleBlock(uint32_t block_address, unsigned char *buf)
{
    int i;

    block_address = block_address << 9;

    CS_UP;
    while (0x00 != sdsc_command(READ_SINGLE_BLOCK, block_address))
        ;

    while (0xfe != spi_rx ())
        ;

    for (i = 0; i < 512; i ++ ){
        //buf [ i ] = spi_rx();
        put_int(spi_rx());
        put_string("\n");
    }
    spi_rx();
    spi_rx();
    CS_DOWN;

    //for (i = 0; i<512; i++) put_int(buf[i]);

The problem is that the printout is:

0 0 0 ..(zeros).. 128 255 255 255 12 255 255 255 0 8 0 0 0 72 59 ..(zeros).. 85 170

Did somebody encounter this problem?

Do you have some suggestions?