cannot load from non-primitive location

Hi,

I try to transmit data. The Expression window show "cannot load from non-primitive location".  What does it mean?

My Code:

uint8 tx_data[8] = {0x11,0x22};
uint8 *tx_ptr = &tx_data[0];

void main(void)
{
    canInit(); //CAN intialisieren

    canTransmit(canREG1, canMESSAGE_BOX1, tx_ptr);

    while(1);
}

Best regards

Dennis