USCI Interrupt Enables being non-user-code reset?

bool read_I2C( void )
{
		i2c_frame.read_write = true;

		// Fill TX buffer
		uint8_t TxData[2];
		TxData[0] = 0x00;	// I2C slave data address beginning at Status
		TxData[1] = (uint8_t)( 0x000F & Status );

		i2c_frame.PTxData = (unsigned char *)TxData;
		i2c_frame.TXByteCtr = sizeof TxData;

		while(UCB0CTL1 & UCTXSTP);		// Ensure stop condition has been sent
		UCB0CTL1 |= UCTR + UCTXSTT;		// TX start condition

		__delay_cycles(10000);
/*
		if( i2c_timeout( &i2c_frame.TXByteCtr ) )
		{
			i2c_frame.num_failures++;
			return 0;
		}
*/

	i2c_frame.read_write = false;	// READ
	i2c_frame.PRxData 	= (unsigned char *)i2c_frame.PRxData;	// RX array start address
	i2c_frame.RXByteCtr = 32;       							// Load TX byte counter
	while (UCB0CTL1 & UCTXSTP);            						// Ensure stop condition got sent
	UCB0CTL1 &= ~UCTR;
	UCB0CTL1 |= UCTXSTT;             							// I2C RX, start condition

	__delay_cycles(5000);

	i2c_start_xchange = false;
}

bool i2c_timeout( volatile uint8_t *ByteCtr )
{
	uint32_t i2c_timeout = 0;

	while( *ByteCtr > 0 )
	{
		__delay_cycles(16); // 1us w/ 16MHz clock
		i2c_timeout++;
		if( i2c_timeout >= 10000) // 10ms
			return 1;	// timeout
	}
	return 0;	// no timeout
}

#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
	if( i2c_frame.read_write )	// I2C TX/write
	{
		if (i2c_frame.TXByteCtr)                // Check TX byte counter
		{
			UCB0TXBUF = *i2c_frame.PTxData++;   // Load TX buffer
			i2c_frame.TXByteCtr--;              // Decrement TX byte counter
		}
		else
		{
			UCB0CTL1 |= UCTXSTP;                // I2C stop condition
			IFG2 &= ~UCB0TXIFG;                 // Clear USCI_B0 TX int flag
		}
	}
	else	// I2C RX
	{
		i2c_rx++;

		i2c_frame.RXByteCtr--;                  // Decrement RX byte counter
		if (i2c_frame.RXByteCtr)
		{
			*i2c_frame.PRxData++ = UCB0RXBUF;   // Move RX data to address PRxData
			if (i2c_frame.RXByteCtr == 1)       // Only one byte left?
			{
				UCB0CTL1 |= UCTXSTP;            // Generate I2C stop condition
			}
		}
		else
		{
			*i2c_frame.PRxData = UCB0RXBUF;     // Move final RX data to PRxData
		}
	}
}