fx_file_open fails to open file

Hi,

in my application I have a file.dat stored on the eMMC. Sometimes I need to update the records inside that file, but the fx_file_open operations fails. My code is:

UINT status;
char fileName[] = "file.dat";

    status = fx_file_open(&g_fx_media0, &g_my_file, (CHAR *)fileName, FX_OPEN_FOR_WRITE);
    if (FX_SUCCESS != status)
        {
            while(1);  
        }

the status variable is not equal to FX_SUCCESS and the execution blocks inside the while(1)  cycle. Anyone has any idea of what am I doing wrong? Perhaps have I to open that file with different options (i.e. append, etc..).
 I'm working with SSP 1.1.0.

Thank you!