msp430f249 UART USCI_A0 missing one character every 2 character

Hello,

i implement UART on USCI_A0 and when i send a file from an hyperterminal on a PC at 115200Kb/s i miss one char every 2 char :

For exemple if PC sends 1,2,3,4,5,6,7.... i receive 1,3,5,7

I have the same problem at 9600b/s

I have the same problem if i disable timer interrupt (no other IT may take over the CPU)

There is no error flag set in UCA0STAT

Here is my UART initialization :

=====================

 
    UCA0CTL1 |= UCSSEL_2;                     // SMCLK
   
    //Baud rate divider with 1MHz = 1MHz/115200 = ~8.7
    UCA0BR0 = 8;                              // 1MHz 115200
    UCA0BR1 = 0;                              // 1MHz 115200

    //In UCA0MCTL: UCBRSx =round( ( 8,7 – INT(8,7) ) × 8 ) = round(0.7*8) = 05
    UCA0MCTL = UCBRS2 + UCBRS0;               // Modulation UCBRSx = 5
   
    UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
      

    IE2 |= UCA0RXIE;                          // Enable USCI_A0 RX interrupt

Here is my UART initialization :

=====================

#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCI0RX_ISR(void)
{
    //if (  UCOE & UCA0STAT)    while(1) {;}
    //if (  UCRXERR & UCA0STAT)    while(1) {;}
   
        static int compteur=0;
        compteur++;
    CVM_RXFIFO[CVM_RXFIFOFIFOWriteIndex]=UCA0RXBUF;
    CVM_RXFIFOFIFOWriteIndex=(CVM_RXFIFOFIFOWriteIndex+1)%CVM_RX_BUFFER_SIZE;
   // P1OUT ^= 0x01;
 }

Here is the clock initialization

=======================

    if (CALBC1_1MHZ ==0xFF || CALDCO_1MHZ == 0xFF)                                    
    { 
        MAIN_T_Error();
        while(1);                               // If calibration constants erased
    }  
    //use calibration 1MHz for MCLK: Master clock and SMCLK: Sub-main clock. SMCLK is selected as DCOCLK
    BCSCTL1 = CALBC1_1MHZ;                    // Set DCO
    DCOCTL = CALDCO_1MHZ;

Have you any idea of what can happen ?

Best regards