Can't use Serial or Wire function at same time?

[water5]

When I use Serial.begin() or Wire.begin() function at same time, the matrix seems not works?

#include <Adafruit_GFX.h>
#include <Adafruit_NeoMatrix.h>
#include <Adafruit_NeoPixel.h>


#ifndef PSTR
 #define PSTR // Make Arduino Due happy
#endif

#define PIN 6

Adafruit_NeoMatrix matrix = Adafruit_NeoMatrix(8, 8, PIN,
  NEO_MATRIX_TOP     + NEO_MATRIX_RIGHT +
  NEO_MATRIX_COLUMNS + NEO_MATRIX_PROGRESSIVE,
  NEO_GRB            + NEO_KHZ800);

const uint16_t colors[] = {matrix.Color(255, 0, 0), matrix.Color(0, 255, 0), matrix.Color(0, 0, 255)};

void setup()
{
  Serial.begin(9600);
  matrix.begin();
  matrix.setTextWrap(false);
  matrix.setBrightness(32);
  matrix.setTextColor(colors[0]);
}

// Can't work?
void loop()
{
  matrix.fillScreen(0);
  matrix.setCursor(0, 0);
  matrix.print(F("1234"));
  matrix.show();

[caternuson]

Where is the call to Wire.begin()?

Or - with the above sketch, there is no output (what does "not work" mean?) on the matrix and you can simply comment out the one line:

  Serial.begin(9600);

and the sketch then works as expected?