curious segmentation faults - c

Question

I wrote a program that worked well without any errors.
I read a text file and write the contents to an array (line by line and seperat strings in this line one by one). Then I added a second textfile and again tried to read the content but then I got some crazy segmentation faults that are only reported when I debug my program.
This is the part of the program that causes the error:
vrFile = fopen("file.txt","r");
//some temporary arrays
float taz[5000], tel[5000], ttime[5000], tvr[5000][nbins], tdbz[5000][nbins];
int size = 1024, pos;
int c;
//buffer for the line to read
char *buffervr = (char *)malloc(size);
int lin=0;
if(vrFile) {
do { // read all lines in file
pos = 0;
do{ // read one line
c = fgetc(vrFile);
if(c != EOF) buffervr[pos++] = (char)c;
if(pos >= size - 1) { // increase buffer length if line is too long - leave room for 0
size *=2;
buffervr = (char*)realloc(buffervr, size);
}
}while(c != EOF && c != '\n');
buffervr[pos] = 0;
// line is now in buffer
char *ptr;
ptr = strtok(buffervr,"\t");
int abs=1;
while(ptr != NULL) {
if(abs==1){
taz[lin] = atof(ptr);
}
else if(abs==2) {
tel[lin] = atof(ptr);
}
else if (abs==3) {
ttime[lin] = atof(ptr);
}
else {
tvr[lin][abs-4]=atof(ptr);
}
abs++;
ptr = strtok(NULL, "\t");
}
lin++;
} while(c != EOF);
fclose(vrFile);
}
//free(buffervr);
The first thing is that I get a segmentation fault when I try to allocate a buffer char *buffervr = (char *)malloc(size);. When I do this before I allocate the arrays float taz[5000], tel[5000], ttime[5000], tvr[5000][nbins], tdbz[5000][nbins]; it works?!
The second thing is that I cant read the file with c = fgetc(vrFile); although I can open it. Here I get another segmentation fault?!
Can someone tell me that went wrong?
Thank you!
EDIT: actual code:
int size = 1024, pos;
int c, cdbz;
char *buffervr = (char *)malloc(size);
char *bufferdbz = (char *)malloc(size);
int lin=0;
char *taz, *tel, *ttime, **tvr, **tdbz;
taz=(char *) malloc(5000*sizeof(char));
tel=(char *) malloc(5000*sizeof(char));
ttime=(char *) malloc(5000*sizeof(char));
tvr = malloc(5000 * sizeof(char *));
int i;
for(i = 0; i < 5000; i++) {
tvr[i] = malloc(nbins * sizeof(char));
}
tdbz = malloc(5000 * sizeof(char *));
for(i = 0; i < 5000; i++) {
tdbz[i] = malloc(nbins * sizeof(char));
}
//float taz[5000], tel[5000], ttime[5000], tvr[5000][nbins], tdbz[5000][nbins];
if(vrFile!=NULL) {
do { // read all lines in file
pos = 0;
do{ // read one line
c = fgetc(vrFile);
if(c != EOF) buffervr[pos++] = (char)c;
if(pos >= size - 1) { // increase buffer length - leave room for 0
size *=2;
buffervr = (char*)realloc(buffervr, size);
}
}while(c != EOF && c != '\n');
buffervr[pos] = 0;
// line is now in buffer
char *ptr;
ptr = strtok(buffervr,"\t");
int abs=1;
while(ptr != NULL) {
if(abs==1){
taz[lin] = (ptr);
}
else if(abs==2) {
tel[lin] = (ptr);
}
else if (abs==3) {
ttime[lin] = (ptr);
}
else {
tvr[lin][abs-4]=(ptr);
}
abs++;
ptr = strtok(NULL, "\t");
}
lin++;
} while(c != EOF);
fclose(vrFile);
}
free(buffervr);
.
.
.
int lins,abss;
for (lins=0; lins<lin; lins++)
{
time[0]=ttime[lins];
az[0]=taz[lins];
el[0]=tel[lins];
for (abss=0; abss<nbins; abss++)
{
vr[abss]=tvr[lins][abss];
//dbZ[abss]=tdbz[lins][abss];
}
}
note: time, lat, lon, az, el and vr are pointers.
EDIT: I solved my Problem this way:
vrFile = fopen("file.txt","r");
if (vrFile != NULL){
while ((getline(&line, &len, vrFile)) != -1) {
NumberOfLines++;
if(NumberOfLines == 1){
line = strtok(line, "\t");
while(line != NULL){
NumberOfDoubles++;
line = strtok(NULL, "\t");
}
}
}
}
rewind(vrFile);
int i,j;
float* taz;
float* tel;
float* ttime;
float** tvr;
float** tdbz;
//1D Arrays
taz = (float*) malloc (sizeof(float)*NumberOfLines);
tel = (float*) malloc (sizeof(float)*NumberOfLines);
ttime = (float*) malloc (sizeof(float)*NumberOfLines);
//2D Arrays
tvr = (float**) malloc (sizeof(float*)*NumberOfLines);
for(i=0;i<NumberOfLines;i++){
tvr[i] = (float*) malloc (sizeof(float)*NumberOfDoubles);
}
tdbz = (float**) malloc (sizeof(float*)*NumberOfLines);
for(i=0;i<NumberOfLines;i++){
tdbz[i] = (float*) malloc (sizeof(float)*NumberOfDoubles);
}
if (vrFile != NULL){
i = 0;
while ((getline(&line, &len, vrFile)) != -1) {
line = strtok(line, "\t");
j = -3;
while(line != NULL){
switch(j){
case -3: taz[i] = strtod(line, NULL);break;
case -2: tel[i] = strtod(line, NULL);break;
case -1: ttime[i] = strtod(line, NULL);break;
default: tvr[i][j] = strtod(line, NULL);break;
}
line = strtok(NULL, "\t");
j++;
}
i++;
}
}