c++ - C++ Program crashes when reading binary data from file of X length

Question

I am trying to read binary data from a file, here is my file structure:

#define SIGNATURE_LENGTH 3
#define VERSION_LENGTH 2
#define DATACOUNT_LENGTH 4
#define COMPRESS_LENGTH 1
#define FORMAT_LENGTH 2
#define DATALENGTH_LENGTH 4

const unsigned char resSignature[SIGNATURE_LENGTH] = { 0x52, 0x45, 0x53 };
const unsigned char resVersion[VERSION_LENGTH] = { 0x01, 0x00 };

const unsigned char isCompressed[COMPRESS_LENGTH] = { 0x01 };
const unsigned char notCompressed[COMPRESS_LENGTH] = { 0x00 };

// Data Formats:
const unsigned char dataUnknown[FORMAT_LENGTH] = { 0x00, 0x00 };
const unsigned char dataXML[FORMAT_LENGTH] = { 0x01, 0x00 };


// Define header structure for resource file
struct ResHeader
{
    unsigned char signature[SIGNATURE_LENGTH];
    unsigned char version[VERSION_LENGTH];
};

// Define data structure for resource file
struct ResData
{
    unsigned char compressed[COMPRESS_LENGTH];
    unsigned char dataFormat[FORMAT_LENGTH];
    unsigned char dataLength[DATALENGTH_LENGTH];
    unsigned char *data;
};

And my class uses:

std::fstream File;

// Resource file makeup
ResHeader  header;
unsigned char dataCount[DATACOUNT_LENGTH];

// Vector to contain resource file data
std::vector<ResData> ResourceData;

The program crashes when I try to read from a file:

int ResourceFile::LoadFile()
{
    File.open("blah.dat", std::ios::in | std::ios::binary);

    // Read header
    File.read((char*) header.signature, SIGNATURE_LENGTH);
    File.read((char*) header.version, VERSION_LENGTH);
    if(!VerifyHeader())
    {
        File.close();
        return HEADER_INCORRECT;
    }
    File.read((char*) dataCount, DATACOUNT_LENGTH);
    long fileCount = unsignedCharArrayToLong(dataCount);
    for(long i = 0; i < fileCount; ++i)
    {
        ResData tmp;
        File.read((char*) tmp.compressed, COMPRESS_LENGTH);
        File.read((char*) tmp.dataFormat, FORMAT_LENGTH);
        File.read((char*) tmp.dataLength, DATALENGTH_LENGTH);
        File.read((char*) tmp.data, unsignedCharArrayToLong(tmp.dataLength));
        ResourceData.push_back(tmp);
    }
    File.close();
    return SUCCESS;
}

The program crashes on the line:

File.read((char*) tmp.data, unsignedCharArrayToLong(tmp.dataLength));

The length of the data in the file is 282, which is what is read into tmp.dataLength; so the number is accurate. The data is also compressed using easy zlib: http://www.firstobject.com/easy-zlib-c++-xml-compression.htm

Any suggestions/help as to what I am doing wrong or what I could be doing better would be appreciated. Thank you.