Another problem with malloc

I thought that I understood malloc, however, the following program aborts and I dont know why



#include <stdio.h>
#include <string.h>
#include <stdlib.h>


#include "uleis_rate.h"
#include "df.h"
#include "mfhdf.h"
#define STEP 100
#define NROWS 100
#define NCOLUMNS 2
#define MAXLINE 80
#define MAX_NAME 11
int decompress8(int);
int decompress16(int);
void get_set(int *tstart, int *tstop, int *type, int *channel, int *sector);
int call_file(int *type, int *ii, int *jj, int *sec, int *cn, int *time);
int control_file(FILE *filename);
int geti(char *);
void main(argc, argv)
int argc;
char *argv[];
{
  int32 hdf_fp,sd_id;
  struct URateSet ratetestdata;
  int ii,jj,kk,cc,dd,zz,retval,flag;
  int time, temp, temp_time;
  int bits, tstart, tstop, sector, channel;
  int rate_type,value;
  int **arr1;
  int number = 0, loop = 0, nrows = NROWS;
  int i,j;
  char ofile[MAXLINE], ctrl_buf[MAXLINE];
  char *ofile_ptr;
  char tempbuf[MAXLINE], *temp_ptr;
  char hold[MAXLINE], *hold_ptr;
  char *namebuf, *name_ptr;
  char firstbuf[MAX_NAME], *first_ptr;
  char *comma_ptr;
  int difference, newline=0;
  FILE       *ofp, *ctrl_ptr;




  if (argc > 3){
      printf("Usage: rd_hdf hdf_file control_file\n");
      exit(1);
    }
  /* open hdf input file */

  puts(" Opening HDF file .");
  if ((hdf_fp=Hopen(argv[1], DFACC_READ, 0))==FAIL){
      fprintf(stderr, "Hopen: could not open hdf file\n");
      HEprint(stdout, 0);
      exit(-1);
    }
  puts(" Starting HDF file ..");
  Vstart(hdf_fp);
  printf(" %u %s %d\n", argv[1], argv[1], argv[1]);
  if ((sd_id=SDstart(argv[1], DFACC_RDONLY))==FAIL){
      fprintf(stderr, "SDstart: could not open hdf file\n");
      exit(-1);
    }

  /* opening control file */
  printf(" value of argc is %d\n", argc);
  if (argc == 2){
    printf(" No control file entered\n");
  }else{
    puts(" A control file was entered");
    if((ctrl_ptr = fopen(argv[2], "r")) == NULL){
      puts(" Error opening control file");
      return;
    }
  }

  puts(" enter output file ");
  gets(ofile);

   if ((ofp = fopen(ofile, "w")) == NULL)
      {puts(" Error opening output file");
       return;
      }      

  puts(" before control file input");
  i = control_file(ctrl_ptr);
  if(i == -1)
    puts(" big time error in control_file reading");
  puts(" after control file input");


   arr1 = (int **)malloc (NROWS * sizeof (int *));
   puts(" after NROWS malloc");
   for (i=0; i< NROWS; i++){
     printf(" malloc'ing row # %d\n", i);
     arr1[i] = (int *)malloc (NCOLUMNS * sizeof (int));
   }

   puts(" after initial malloc");
  init_rd_uleis_rate(hdf_fp, sd_id);
  puts(" after initialization of hdf file ");
 
  get_set(&tstart, &tstop, &rate_type, &channel, &sector);

  fprintf(ofp,"%10s %10s %10s %10s\n", "time", "sector", "channel", "number");

   printf(" arr1 = %u\n", arr1);

  for (ii=tstart; ii<tstop; ii++){
    for (jj=0; jj<10; jj++){
      value = call_file(&rate_type, &ii, &jj, &sector, &channel, &time);
      if (loop <  100){
        arr1[number][0] = time;
        arr1[number][1] = value;
        loop++;
      }
      else {
        loop = 0;
        nrows += NROWS;
        printf("Dynamically allocating %u to size %d\n",arr1, nrows);
        arr1 = (int **)realloc (arr1, nrows * sizeof (int *));
        for (i=0; i<nrows-NROWS; i++)
          arr1[i] = (int *)realloc(arr1[i], NCOLUMNS * sizeof (int));
        for (i=nrows-NROWS;i<nrows;i++)
          arr1[i] = (int *)malloc(NCOLUMNS * sizeof (int));
        arr1[number][0] = time;
        arr1[number][1] = value;
        loop++;
      }
      number++;
    }
  }
  for (i=0;i<number;i++)
    fprintf(ofp, "%10d %10d %10d %10d\n", arr1[i][0], sector,
            channel, arr1[i][1] );



  /* all done, close HDF file */

  close_rd_uleis_rate();
  fprintf(stdout,"\nVS detached \n");
  Vend(hdf_fp);
  fprintf(stderr,"VS ended \n");
  if (Hclose(hdf_fp)==FAIL){
      fprintf(stderr, "Hclose: could not close hdf file\n");
      exit(-1);
  }
  fprintf(stderr,"file closed \n");
  if(fclose(ofp) != 0)
      {puts(" error closing output file");
      }  
  if(fclose(ctrl_ptr) != 0)
      {puts(" error closing control file");
      }  

  exit(0);
}


The output from the program is as follows:

urate_rd uleis.hdf first.ctrl
 Opening HDF file .
 Starting HDF file ..
 4026530629 uleis.hdf -268436667
 value of argc is 3
 A control file was entered
 enter output file
out.txt
 before control file input
# lines beginning with a # are comment lines
 
#       another comment line
 
 
 
CHANNEL, 2,8,3,2,0,
 
 inside channel CHANNEL
 inside channel 2
 inside channel 8
 inside channel 3
 inside channel 2
 inside channel 0
 
 
OUTPUT_FILE, out.txt,
 
 inside output_file OUTPUT_FILE
 inside output_file out.txt
 
 
HAPPY, dummy,    really dum,   garbage,
 inside happy HAPPY
 inside happy dummy
 inside happy really dum
 inside happy garbage
 after control file input
 after NROWS malloc
 malloc'ing row # 0
 malloc'ing row # 1
 malloc'ing row # 2
Bus error (core dumped)




Any advise on why this is aborting, how to fix it, and any help on whether this is the best way to use malloc for two dimensional/three dimensional arrays would be very helpfull

Thanks Dennis