Trouble with I2C communication msp430 Slave ->Master

I am having some trouble with I2C working consistently. I am using the msp430g2553 as a slave and having it receive messages from a master Arduino. Upon receiving a command the slave msp sends a 'D' over the i2c line.

#define NUM_BYTES  32                    // How many bytes?
char *PRxData,*Start;                     // Pointer to RX data
volatile unsigned char TXByteCtr, RXByteCtr, RX = 0;
char RxBuffer[32];       // Allocate 128 byte of RAM
void I2C_init()
{
    WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
    P1SEL |= BIT6 + BIT7;                     // Assign I2C pins to USCI_B0
    P1SEL2|= BIT6 + BIT7;                     // Assign I2C pins to USCI_B0
    UCB0CTL1 |= UCSWRST;                      // Enable SW reset
    UCB0CTL0 = UCMODE_3 + UCSYNC;             // I2C Slave, synchronous mode
    UCB0I2COA = 0x48;                         // Own Address is 048h
    UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
    UCB0I2CIE |= UCSTPIE + UCSTTIE;           // Enable STT and STP interrupt
}

void main()

{

while(1)
    {
        RX = 1;
        IE2 &= ~UCB0TXIE;                         // Disable TX interrupt
        IE2 |= UCB0RXIE;                          // Enable RX interrupt
        TXByteCtr=0;
        RXByteCtr=0;
        PRxData = (char *)RxBuffer;    // Start of RX buffer
        Start= RxBuffer;
        __bis_SR_register(CPUOFF + GIE);        // Enter LPM0 w/ interrupts
        _disable_interrupt();

        //Process data obtained

       _enable_interrupt();
        RX=0;
        IE2 |= UCB0TXIE;
        IE2 &= ~UCB0RXIE;

     }

}

#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
  if(RX == 0)
  {
      UCB0TXBUF = 'D';      // Transmit data at address PTxData
      TXByteCtr++;                              // Increment TX byte counter
  }
  if(RX == 1){*PRxData++ = UCB0RXBUF;       // Move RX data to address PRxData
  RXByteCtr++;                              // Increment RX byte count
  if(RXByteCtr >= NUM_BYTES){               // Received enough bytes to switch
      __bic_SR_register_on_exit(CPUOFF);       // Exit LPM0 if data was
  }
 }
}

#pragma vector = USCIAB0RX_VECTOR
__interrupt void USCIAB0RX_ISR(void)
{
  if(RX == 0){ UCB0STAT &= ~(UCSTPIFG + UCSTTIFG);       // Clear interrupt flags

}
  if(TXByteCtr)
  {
      IE2 &= ~UCB0TXIE;
  }
  if(RX == 1){UCB0STAT &= ~(UCSTPIFG + UCSTTIFG);       // Clear interrupt flags
  }

}

It would be of great help if someone could tell me how to get this working consistently.