Neo hangs on delayMicroseconds

Code:

  Serial.println(i);
  digitalWrite(clk, LOW);
  digitalWrite(dio, value & 0x01 ? HIGH : LOW);
  Serial.println("delay");
  delayMicroseconds(3);
  Serial.println("shift");

Never reaches 'shift'.

 

Code:

void setup() {
  Serial.begin(115200);
  delay(100);
  // initialize digital pin 13 as an output.
  pinMode(13, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for a second
  digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
  Serial.println("A");
  delayMicroseconds(3);              // wait for 3 microseconds
  Serial.println("B");
{

This is giving me no issues, but only if I start with delayMicroseconds(3000); and go down to 3. If I then load an empty sketch into the M4 and load the above sketch it fails completely.