memcpy Crash

stock QSortAssoc(numbers[][], sort_index, left, right, pivot[], len)
{
    new
//      pivot   = numbers[left],
        l_hold  = left  ,
        r_hold  = right ;

    memcpy(pivot, numbers[left], 0, len * 4, len);
    // A print tells me it crashes here; this is consistent


    while (left < right)
    {
        while ((numbers[right][sort_index] >= pivot[sort_index]) && (left < right)) right--;
        if (left != right)
        {
            memcpy(numbers[left], numbers[right], 0, len * 4, len);
            left++;
        }
        while ((numbers[left][sort_index] <= pivot[sort_index]) && (left < right)) left++;
        if (left != right)
        {
            memcpy(numbers[right], numbers[left], 0, len * 4, len);
            right--;
        }
    }

    memcpy(numbers[left], pivot, 0, len * 4, len);

    pivot[sort_index] = left;

    left    = l_hold;
    right   = r_hold;

    if (left < pivot[sort_index]) QSortAssoc(numbers, sort_index, left, pivot[sort_index] - 1, pivot, len);
    if (right > pivot[sort_index]) QSortAssoc(numbers, sort_index, pivot[sort_index] + 1, right, pivot, len);
}