MSP430F5438A: External crystal problem

Hi,

#include <msp430.h>

int main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

P11DIR = BIT1+BIT2+BIT0; // P11.1-2 to output direction
P11SEL |= BIT1+BIT2+BIT0; // P11.1-2 to output SMCLK,MCLK
P5SEL |= 0x0C; // Port select XT2

UCSCTL6 &= ~XT2OFF;

UCSCTL3 |= SELREF_2; 

UCSCTL4 |= SELA_2;

do
{
UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + XT1HFOFFG + DCOFFG);

SFRIFG1 &= ~OFIFG;

}while (SFRIFG1&OFIFG);

UCSCTL6 &= ~XT2DRIVE0; 

UCSCTL4 |= SELS_5 + SELM_5; 

while(1); 
}

This is my code for set External crystal (XT2=12MHZ)  ,here i debug the code  the external crystal is perfectly work.

But switch off the board and on(reset) the Clock goes to 1MHZ .

What the reason for this one problem?