Problem with character strings in a delimeted buffer class

I am working on a class that takes a person object, then packs it to a buffer and writes it to a file.  The problem is that when I try to read it back into the buffer from the file, I get a runtime error.  Here is a copy of the significant functions:

Any help would be appreciated


Here are the pack and unpack functions in my person class:


int Person::Pack (IOBuffer & Buffer) const
{// pack the fields into a FixedFieldBuffer,
 // return TRUE if all succeed, FALSE o/w
      int numBytes;
      Buffer . Clear ();
      numBytes = Buffer . Pack (FirstName);
      if (numBytes == -1) return FALSE;
      numBytes = Buffer . Pack (LastName);
      if (numBytes == -1) return FALSE;
      numBytes = Buffer . Pack (IDNumber);
      if (numBytes == -1) return FALSE;

      return TRUE;
}


int Person::Unpack (IOBuffer & Buffer)
{

      Clear ();
      int numBytes;
      numBytes = Buffer . Unpack (FirstName);
cout << numBytes;
      if (numBytes == -1) return FALSE;
      FirstName[numBytes] = 0;
      numBytes = Buffer . Unpack (LastName);
      if (numBytes == -1) return FALSE;
      LastName[numBytes] = 0;
      numBytes = Buffer . Unpack (IDNumber);
      if (numBytes == -1) return FALSE;
      IDNumber[numBytes] = 0;
      return TRUE;
}



Here is the unpack from  delimited buffer:

int DelimFieldBuffer :: Pack (const void * field, int size)
// set the value of the next field of the buffer;
// if size = -1 (default) use strlen(field) as Delim of field
// return number of bytes packed, -1 if error
{
      // look for delimeter in field!
      short len; // length of string to be packed
      if (size >= 0) len = size;
      else len = strlen ((char*)field);
      if (len > (short)strlen((char*)field)) // field is too short!
            return -1;
      int start = NextByte; // first character to be packed
      NextByte += len + 1;
      if (NextByte > MaxBytes) return -1;
      memcpy (&Buffer[start], field, len);
      Buffer [start+len] = Delim; // add delimeter
      BufferSize = NextByte;
      return len;
}

int DelimFieldBuffer :: Unpack (void * field, int maxBytes)
// extract the value of the next field of the buffer
// return the number of bytes extracted, -1 if error
{
      
      int len = -1; // length of packed string
      int start = NextByte; // first character to be unpacked
      for (int i = start; i < BufferSize; i++)
            if (Buffer[i] == Delim)
                  {len = i - start; break;}
      if (len == -1) return -1; // delimeter not found
      NextByte += len + 1;
      if (NextByte > BufferSize) return -1;
      // check for maxBytes

      memcpy (field,&Buffer[start] , len);      
      if (maxBytes > len || maxBytes == -1)
  ((char*)field) [len] = 0; // zero termination for string
      return len;
}



and here is the test:



      // Test writing
      //Buff . Print (cout);
      ofstream outfile (myfile,ios::out);
      result = Buff . WriteHeader (outfile);
      cout << "write header "<<result<<endl;
      person1 . Pack (Buff);
      //Buff . Print (cout);
      recaddr1 = Buff . Write (outfile);
      cout << "write at "<<recaddr1<<endl;
      person2. Pack (Buff);
      //Buff . Print (cout);
      recaddr2 = Buff . Write (outfile);
      cout << "write at "<<recaddr2<<endl;
      person3. Pack (Buff);
      //Buff . Print (cout);
      recaddr3 = Buff . Write (outfile);
      cout << "write at "<<recaddr3<<endl;
      outfile . close ();

      // test reading

      ifstream infile (myfile, ios::in);
      result = Buff . ReadHeader (infile);

      cout <<"read header "<<result<<endl;

Buff . DRead (infile,recaddr3);
      person . Unpack (Buff);
      person . Print (cout, "First record:");
      Buff . DRead (infile, recaddrw);
      person . Unpack (Buff);
      person . Print (cout, "Second record:");