c - C: Why am I getting 'Floating Point Exception: 8' From This Calculation?

Question

Here is my function:

int scoreString(char *toScore) {
    int length = strlen(toScore);
    int score = 0;
    int spaceCount = 0;
    for (int i = 0; i < length; i++) {
        char current = toScore[i];
        if (current == ' ') {
            spaceCount++;
        }
        score += scoreChar(current);
    }
    //English words are ~5 characters
    int charsPerWord = (length/(spaceCount + 1));
    if (charsPerWord >=3 && charsPerWord <= 7) {
        //Big Bonus
        score = score * 2; //THIS LINE CAUSES PROBLEMS
    } else if (spaceCount <= 1) {
        //Big penalty
        score = score / 2; //THIS LINE CAUSES PROBLEMS
    }
    return score;
}

If I get ride of the two lines that are marked as causing problems, everything is dandy. The output of this function without them ranges from 100-2000 on the input I'm testing so this should not be an overflow error ... if I leave either of those two lines in I get Floating point exception: 8 after a few executions. Any ideas?