fgets returns invalid parameter error

[SteveTaylor]

Okay I have tried some more changes and the following is causing the same issue. The input file has about 90 entries and this stopped working on the 62nd:

while (5 == fscanf(fraw, "%lu %lu %lu %lu %lu", &D1,     &D2,   &D3,  &D4,     &D5))

    {
        linesWritten++;
        fprintf(ffor,"%lu, %lu, %lu, %lu, %lu, %lu\n",
                    D1,
                    D2,
                    (D1- D2),
                    (D3- D2),
                    (D4- D1),
                    (D5- D1));
    }

This is the input file format:

2267924448 242996103589964 242996103591341 242996103591477 242996103609081
2267927216 242996103663243 242996103664688 242996103664798 242996103670621
2267946020 242996104269242 242996104271350 242996104271494 242996104291682

The last line is the one that failed, all of the lines are formatted the same as these three.