UARTprintf lost charaters

Hi,

I copy the program from the example of qs-rgb in LM4F120,

int
main(void)
{
  unsigned long ulStatus;
    unsigned long ulResetCause;
    long lCommandStatus;
 
  //
    // Enable stacking for interrupt handlers.  This allows floating-point
    // instructions to be used within interrupt handlers, but at the expense of
    // extra stack usage.
    //
    ROM_FPUEnable();
    ROM_FPUStackingEnable();

    //
    // Set the system clock to run at 40Mhz off PLL with external crystal as
    // reference.
    //
    ROM_SysCtlClockSet(SYSCTL_SYSDIV_5 | SYSCTL_USE_PLL | SYSCTL_XTAL_16MHZ |
                       SYSCTL_OSC_MAIN);

    //
    // Enable the hibernate module
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_HIBERNATE);

    //
    // Enable and Initialize the UART.
    //
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
    ROM_GPIOPinConfigure(GPIO_PA0_U0RX);
    ROM_GPIOPinConfigure(GPIO_PA1_U0TX);
    ROM_GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);
    UARTStdioInit(0);

  UARTprintf("Welcome to the Stellaris LM4F120 LaunchPad!\n");
    UARTprintf("Type 'help' for a list of commands\n");
    UARTprintf("> ");

}

but from the console, it just print

Welcome to the Ste

and then panic, it looks so strange! only 18 charaters.