SOLVED: Problem compiling code error: "undefined Reference to 'Timer1'"

Ah, I see you do have timer1.initialise in your setup section;

void setup()
{
//longest pulse rep period in PPM is usally 20 milliseconds,
// initialize timer1, and set a 22ms second period(22000us)
    Timer1.initialize(MaxPulseWait);

So, we need to dig a little deeper here then,

Paul