AVR-Chat

#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>
#include "uart.h"

int main(void){

   PORTB=0xFF;
   DDRB=0xFF;
   PORTD=0xFF;
   DDRD=0xFF;

   uart_init( UART_BAUD_SELECT(19200,9216000) );
   sei();

   for (;;){
      PORTB=0x00;
      PORTB=0xFF;
      PORTD=0x00;
      PORTD=0xFF;
      uart_puts("AT");
   }
}

This simple code, works fine like is it, but! if i remove the 
blinking ports (PORTB=0x00; PORTB=0xFF;), the 2313 does not send 
anything! Why?
I use Avredit, and this is the first time that I encounter this 
problem in UART.
Is the Watchdog?