problem with keil file system middleware

hi to all,
i am working on project that in it i need to read and write to micro-sd-card in unit of sector, for done that i decide use keil file system middleware and then use fs_ioc_read_sector and fs_ioc_write_sector function that provided by keil.
after following steps that keil provided(good job keil) now i can successfully read sector from sd card with fs_ioc_read_sector function, but when i use fs_ioc_write_sector function to write a sector to sd card it return an fs_error and it dose not write to sd card.
my mcu is lpc1788, i use 4-bit mci bus.
now can any one help me to find a solution for that??
my code is as below:

fsStatus stat;

uint32_t param_status;
if(finit ("M0:") != fsOK)
{
     return -1;
}

drv_id = fs_ioc_get_id ("M0:");

if(drv_id < 0U)
        return -1;

param_status = 0U;                    // Parameter for function call is 0
                                       // Initialize media
if (fs_ioc_device_ctrl (drv_id, fsDevCtrlCodeControlMedia, ¶m_status) != fsOK) {
    return -1;                             // Exit if failed
}

if (fs_ioc_lock (drv_id)) {           // Lock media for USB usage
    return -1;                             // Exit if failed
}

stat = fs_ioc_write_sector (drv_id, 1, buf, 1);

if (stat != fsOK) {                  // = fs_error
    return -1;
}
fs_ioc_unlock(drv_id);
return 1;