Serial.print() gone wild?

Hello,
I am making a data logger using the ADIS16367 from Analog Devices, and saving to an SD card. I use a timer interrupt to sample the sensor and it creates a String object. In the loop, after a certain number of samples, I convert it to a char array and print to the SD card. However, after the SD card initializes and it begins to read the sensor it keeps printing:

Initializing SD card...Initializing SD card...Initializing SD card...Initializing SD card...Initializing SD card...Initializing SD card...

What's up with that?!
It is supposed to print once at the top, but then it should be gone, so I have no idea what is going on here... any ideas/advice?

Thanks for any help in advance!

#include <SD.h>
#include <SPI.h>
#include "TimerOne.h"

#define VERBOSE 1              // 1 to print to serial, 0 to not
#define SAMPLES_PER_WRITE 2    // samples per write to SD card
#define FS 1                  // sample frequency (Hz)
#define TIME 5                 // time to sample (s)

//Sensor's memory register addresses:
const byte SUPPLY_OUT = 0x02;    // Power supply reading
...
const byte SERIAL_NUM = 0x58;    // Serial number

//Sensor commands
const byte READ = 0b00000000;    // ADIS16367 read command (2 bytes)
const byte WRITE = 0b10000000;   // ADIS16367 write command
const byte BURST_READ = 0x3E;    // ADIS16367 burst read command

// pins used for the connections
const int dataReadyPin = 2;
const int ADIScs = 7;
const int SDcs = 8;

volatile byte samplecounter = 0;
volatile unsigned int counter = 0;
String dataString = "time(ms) sensors...\r\n";

void setup()
{
  Serial.begin(115200);
  Serial.print("Initializing SD card...");
  Serial.flush();
  // make sure that the default chip select pin is set to
  // output, even if you don't use it:
  pinMode(10, OUTPUT);
  
  // start communication with SD card
  pinMode(SDcs, OUTPUT);
  if (!SD.begin(SDcs)) {
    Serial.println("Card failed, or not present");
    while(1);
  }
  Serial.println("card initialized.");
  
  // start SPI communication with ADIS16367
  SPI.begin();
  pinMode(ADIScs, OUTPUT);
  digitalWrite(ADIScs, HIGH);
  SPI.setClockDivider(SPI_CLOCK_DIV16);
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode(SPI_MODE3); // set SPI mode 3

  // start Timer1
  Timer1.initialize((1000000UL/FS)); // Start timer at FS Hz
}

void loop()
{
  Serial.flush();
  Serial.println("Type any character to start");
//  String dataString = 'time(ms) sensors...\r\n';
  while (!Serial.available());
  digitalWrite(SDcs, LOW);

  char filename[] = "datalog.txt";
  if(SD.exists(filename)){SD.remove(filename);Serial.print(filename);Serial.println(" removed...");}

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  File dataFile = SD.open(filename, FILE_WRITE);
  if(!dataFile) { // if the file isn't open, pop up an error
    Serial.println("error opening datalog.txt");
    while(1);
  }
  
  Serial.println("Begin logging...");
  Timer1.attachInterrupt(burstReadString2);  // attaches timer overflow interrupt
  unsigned int start = millis();
  String writeString = " ";
  while( (millis()-start) < (TIME*1000) ){
    if(samplecounter>SAMPLES_PER_WRITE) {
      // Move data to new buffer String and erase old data
      writeString = dataString;
      dataString = " ";
      samplecounter = 0;
      // Convert String to string (char array)
      int strlen = writeString.length();
      char string[strlen+1];
      for(int jj=0 ; jj<strlen ; jj++) {
        string[jj] = writeString.charAt(jj);
      }
      // Make sure the string is ended correctly
      string[strlen] = '\0';
      // Write it to SD card
//      dataFile.write(string);
//      if(VERBOSE) Serial.print(string);
//      Serial.print(string);
    }
  }
  Timer1.detachInterrupt();
  dataFile.close();
  Serial.println("Logging complete");
  Serial.println(millis()-start);
  Serial.println();
  // Finish and don't do anything
  while(1);
}




//Sends a burst read command to ADIS16367
// and create String
void burstReadString2(void) {
//  dataString += "woot!\r\n";
  word data = 0;
  // take the chip select low to select the device:
  digitalWrite(ADIScs, LOW);
  digitalWrite(SDcs,HIGH);
  while(digitalRead(dataReadyPin)); //Wait if the pin is low
  Serial.println(samplecounter,HEX);
  int now = millis()/1000;
  dataString += String(now,HEX)+" ";
  // transfer burst read command
  SPI.transfer(BURST_READ); // tell it to begin burst read
  SPI.transfer(0x00);
  delayMicroseconds(4);
  // Get SUPPLY_OUT reading
  data = SPI.transfer(0x00)<<8;  // read high byte
  data |= SPI.transfer(0x00);    // and add on low byte
  data &= 0b0000111111111111;    // make sure it is only 12 bits
  dataString += String(data,HEX);
  // Get gyro and accelerometer readings
  for( int ii=0 ; ii<6 ; ii++) {   // for every register to read
    data = SPI.transfer(0x00)<<8;  // read high byte
    data |= SPI.transfer(0x00);    // and add on low byte
    data &= 0b0011111111111111;    // make sure it is only 14 bits
    dataString += " ";
    dataString += String(data,HEX);
  }
  // Get temperature
  for( int ii=0 ; ii<3 ; ii++) {   // for every register to read
    data = SPI.transfer(0x00)<<8;  // read high byte
    data |= SPI.transfer(0x00);    // and add on low byte
    data &= 0b0000111111111111;    // make sure it is only 12 bits
    dataString += " ";
    dataString += String(data,HEX);
  }
  // Skip ADC data
  SPI.transfer(0x00);
  SPI.transfer(0x00);
  // take the chip select high to de-select:
  digitalWrite(ADIScs, HIGH);
  digitalWrite(SDcs,LOW);
  dataString += "\r\n";
  samplecounter++;
  counter++;
//  Serial.println(counter,DEC);
}

Try to strip the program to a minimal version that does show this same problem, and post it again.

Other issue that can be is that there is a shortcut somewhere on a shield that connects pin8 (SD card) to the reset pin somehow. Time for a visual inspection of the hardware ?

my 2 cents,