[gnormhurst]

I'm using <stdio.h> and not "printf_lib.h". Is that what you meant?

My InterruptHandlerLow() is the usual:

void InterruptHandlerLow ()     
{
	if (PIR1bits.RC1IF && PIE1bits.RC1IE) // rx1 interrupt?
	{
		#ifdef ENABLE_SERIAL_PORT_ONE_RX
		Rx_1_Int_Handler(); // call the rx1 interrupt handler (in serial_ports.c)
		#endif
	}                              
	else if (PIR3bits.RC2IF && PIE3bits.RC2IE) // rx2 interrupt?
	{
		#ifdef ENABLE_SERIAL_PORT_TWO_RX
		Rx_2_Int_Handler(); // call the rx2 interrupt handler (in serial_ports.c)
		#endif
	} 
	else if (PIR1bits.TX1IF && PIE1bits.TX1IE) // tx1 interrupt?
	{
		#ifdef ENABLE_SERIAL_PORT_ONE_TX
		Tx_1_Int_Handler(); // call the tx1 interrupt handler (in serial_ports.c)
		#endif
	}                              
	else if (PIR3bits.TX2IF && PIE3bits.TX2IE) // tx2 interrupt?
	{
		#ifdef ENABLE_SERIAL_PORT_TWO_TX
		Tx_2_Int_Handler(); // call the tx2 interrupt handler (in serial_ports.c)
		#endif
	}
}

I'm not sure exactly how the various ENABLE_SERIAL_PORT_xxx_xx macros are set (I don't have a copy of the code with me) -- I'll have to check. But even if all four were enabled, that should not do bad things, should it?

And why should the startup conditions after download be different than after a reset?