Reset USCI UART MODE

Hi,

I have a problem when i try to reset my uscia. I am doing this between sent packages but the last byte is sent is modified...

I am doing the following in my isr:

#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{

if((IFG2&UCA0TXIFG)&&(IE2&UCA0TXIE)) //INTERRUPCION SERIAL
{

if ( contador_bytes_out != total_bytes_out)
{
UCA0TXBUF = mensaje_out[contador_bytes_out]; // TX next character
contador_bytes_out++;
}
else
{

contador_bytes_out = 0;

IE2 &= ~UCA0TXIE;

__bic_SR_register_on_exit(LPM3_bits); // Exit LPM0


}

}

}

When i get out of the ISR i turn off the USCIA: 

UCA0CTL1 |= UCSWRST;

What do you suggest?

I need this to reduce my power consumption on idle state...