Serial Port on MSP430F47176 and Low Power Modes

I am running different low power modes depending upon what the system is doing. I have another project where I am always in low power mode unless I receive an interrupt from my serial port. In the later case my serial port works fine. But in the prior case it never interrupts. I'm using the same sample code from TI for both cases:

	FLL_CTL0 |= XCAP0PF;                     	// Configure load caps - in this case set to zero because the crystal being used already has the necessary capacitance and doesn't need any additional from the part.
	do
	{
		IFG1 &= ~OFIFG;                         				// Clear the oscillator fault interrupt flag that can file due to switching from LFXT1 to LF. This is to be sure wait for this to clear itself.
		for (iIndex = 0x47FF; iIndex > 0; iIndex--);           	// Allows enough time for the fault to set in the event that it does, so that it's not missed during this check.
	}
	while ((IFG1 & OFIFG));                   // Is the fault still set? The wait until it clears.

	//Configure Serial Port
	P2SEL |= BIT4+BIT5;                       	// P2.4,5 = USCI_A0 RXD/TXD
	UCA0CTL1 |= UCSSEL_1;                     	// CLK = ACLK
	UCA0BR0 = 0x03;                           	// 32k/9600 - 3.41
	UCA0BR1 = 0x00;                           	//
	UCA0MCTL = 0x06;                         	// Modulation
	UCA0CTL1 &= ~UCSWRST;                     	// **Initialize USCI state machine**
	IE2 |= UCA0RXIE;                          	// Enable USCI_A0 RX interrupt

The only difference is that I'm turning off the watchdog for the one that is working and not for the one that is not working. Do I need tell the serial port when I change LPMx modes? 

Thanks