Control keeps falling through cin

[Cube777]

Hi there, I'm trying to write a decrypting/encrypting program. It uses a seed (uses it as a password of some sort) to generate random shifts for the ACSII values of the characters. The problem is as soon as you enter a space in the string you need to encrypt, the cin falls through when it asks for the seed (rendering it useless). I have read about the cin.ignore function but I'm unsure how to use it here. The program works perfectly if the string doesn't include a space but not otherwise. Any help would be greatly appreciated, thanks!

#include <cstdlib>
#include <cstdio>
#include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

void Encrypter()
{
    cout << "Insert a string to encrypt: ";
    std::string cOriginal_string;
    std::cin>> cOriginal_string;
    int nSeed=0;
    cin.clear();
    cout << "Insert seed: ";
    std::string cSeed;
    cin>> cSeed;
    for (int nIndex=0; cSeed[nIndex]!='\0'; nIndex++)
    {
        nSeed+=int(cSeed[nIndex]);
    }
    srand(nSeed);
    std::string cString_changed=cOriginal_string;
    for (int nIndex=0; cOriginal_string[nIndex]!='\0'; nIndex++)
    {
        int nShift_temp=rand()%94+32;
        int nASCII_number=int(cOriginal_string[nIndex]);
        nASCII_number+=nShift_temp;
        if (nASCII_number<127)
        {
            cString_changed[nIndex]=char(nASCII_number);
        }
        else
        {
            cString_changed[nIndex]=char((nASCII_number-126)+32);
        }
    }
    cout << endl << "The string encrypted is: [" << cString_changed << "]" << endl;
}

void Decrypter()
{
    cout << "Insert a string to decrypt: ";
    std::string cOriginal_string;
    std::cin>> cOriginal_string;
    int nSeed=0;
    cin.clear();
    cout << "Insert seed: ";
    std::string cSeed;
    cin>> cSeed;
    for (int nIndex=0; cSeed[nIndex]!='\0'; nIndex++)
    {
        nSeed+=int(cSeed[nIndex]);
    }
    srand(nSeed);
    int nTemp_shift;
    int nASCII_number;
    std::string cChanged_string=cOriginal_string;
    for (int nIndex=0; cOriginal_string[nIndex]!='\0'; nIndex++)
    {
        nASCII_number=int(cOriginal_string[nIndex]);
        nTemp_shift=rand()%94+32;
        nASCII_number=nASCII_number-nTemp_shift;
        if (nASCII_number>31)
        {
            cChanged_string[nIndex]=char(nASCII_number);
        }
        else
        {
            cChanged_string[nIndex]=char(nASCII_number+126-32);
        }
    }
    cout << "The string decrypted is: [" << cChanged_string << "]" << endl;
}

int main()
{
    cout << "This program encrypts or decrypts a string." << endl << endl;
    while (true){
    cout << "Do you want to encrypt or decrypt? (E/D): ";
    char cAnswer;
    cin >> cAnswer;
    if (cAnswer=='e' || cAnswer=='E')
    {
       Encrypter();
    }
    else
    {
        Decrypter();
    }
    cout << endl << "Do you want to do another encryption/decryption?(Y/N): ";
    cin>> cAnswer;
    if (cAnswer=='y' || cAnswer=='Y')
    {
        continue;
    }
    else
    {
        break;
    }
    cout << endl;
    }
    system("PAUSE");
    return 0;
}

Thanks!