Timeout writing SD Card after repeating

I'm stuck with my SD design. 
When i'm writing a single block/sector, no problem. 
Or when i'm writing multiple block /sectors with the multiple_block_write command, no problem. 

But when I repeat the command every single time (bursting a lot of data) i have a timeout on checking the 'DRRDY' bit.
With the single_block i get around 50 blocks a error

example: 
write_mult_block (xx blocks) => No error
Write_mult_block  (xx blocks) => error
write_mult_block  (xx blocks  ) => no error

But when i do this: 
- write (80 blocks) => No error
- printf()
- write (80 blocks) => No error

My  code: 

[/code]

//=====================================================================================================

uint32_t MMCSD_writeBlock(unsigned int baseAddr, uint32_t in_block, uint32_t count,  uint32_t *src_buffer)
{
 uint32_t rtn;

	uint32_t i, j, cnt, s;

	//printf("MMCSD_writeBlock %d %x\n", in_block, src_buffer);

	//USTIMER_delay(1000);

	// reset fifo and config for transmit.
	SETBIT(baseAddr + MMCSD_MMCFIFOCTL, FIFORST);
	USTIMER_delay(100);
	SETBIT(baseAddr + MMCSD_MMCFIFOCTL, FIFODIR);


	// Tell the controller how much to expect
	HWREG(baseAddr + MMCSD_MMCNBLK) = count;



	for (j = 0; j < 8; j++)
		HWREG(baseAddr + MMCSD_MMCDXR) = *src_buffer++;



	if (count == 1) {
		rtn = sendCmd(baseAddr, DMATRIG| WDATX | DTRW | MMCSD_CMD_WRITE_SINGLE_BLOCK, in_block * MMCSD_DEFAULT_BLKLEN, 0); //
	}
	else {
		rtn = sendCmd(baseAddr, DMATRIG| WDATX | DTRW | MMCSD_CMD_WRITE_MULT_BLOCK, in_block * MMCSD_DEFAULT_BLKLEN, 0);
	}

	if (rtn != ERR_NO_ERROR){
		printf("command timeout on sector: %d\n", in_block);
		return (rtn);
	}


	for (s = 0; s < count; ++s) {

			// write the data to the fifo.
			for (i = 0; i < 16; i++)
			{
				cnt = 0;

				// wait for transmit buffer to be ready.
				while (!CHKBIT(baseAddr + MMCSD_MMCST0, DXRDY))
				{
					if (cnt++ > RW_TIMEOUT)
					{
						// timed out waiting for data.
						printf("timeout transmit buffer ready@ sector: %d , count: %d, s: %d \n", in_block, count, s);
						return (ERR_TIMEOUT);
					}
				}

				// copy data to fifo.
				for (j = 0; j < 8; j++)
					HWREG(baseAddr + MMCSD_MMCDXR) = *src_buffer++;
			}

	}

		// confirm the data transfer is complete.
		cnt = 0;
		while (!CHKBIT(baseAddr + MMCSD_MMCST0, DATDNE))
		{
			if (cnt++ > RW_TIMEOUT)
			{
				// timed out waiting for data.
				printf("timeout confirm the data transfer @ sector: %d  , count: %d \n", in_block, count);
				return (ERR_TIMEOUT);
			}
		}

	if (count > 1) {
		rtn = sendCmd(baseAddr, MMCSD_CMD_STOP_TRANSMISSION, 0, 0);
		if (rtn != ERR_NO_ERROR)
			USTIMER_delay(20);
			return (rtn);
	}



	return (ERR_NO_ERROR);
}

[/code]

//=====================================================================================================

What do i miss? 
I'm not using any interrupt, and it is in CPU modus, no DMA 
Its on a TMS320c6748 (Developboard & custom design board)

regards,

Pieter