Array Program Getting Error

[codymahen]

I have all the proper code and when I run it, it just keeps looping when you enter the letters. I also used a function to make it so you could enter both capital and lowercase letters. It did not work and I got an error saying guess() was corrupted. I am completely past my knowledge at point and any help would be great!
Thanks!

  #include <iostream>
using namespace std;

const int NUM_PEGS = 4;
class MasterMind
{
public:
       MasterMind();
       void gameLoop();
       int numAllRight(char guess[]);
       int numHalfRight(char guess[]);
       bool isGoodGuess(char guess[]);
private:
       char secret[NUM_PEGS];
};

int main()
{
	MasterMind brain;
	brain.gameLoop();

	return 0;
}

MasterMind::MasterMind()
{
	for(int i=0; i<4; i=i+1){
		switch(rand()%5)
		{
		case 0:
			secret[i]= 'B';
			break;
		case 1:
			secret[i]= 'R';
			break;
		case 2:
			secret[i]= 'G';
			break;
		case 3:
			secret[i]= 'P';
			break;
		case 4:
			secret[i]= 'Y';
			break;
		}
	}
}

void MasterMind::gameLoop()
{
	char guess[NUM_PEGS];
	cout << "What color pegs(in numerical order)???\n";
	cin >> guess;
	while(!isGoodGuess(guess))
	{
		cout << "Please re-enter your guess\n";
		cin >> guess;
	}


}

int MasterMind::numAllRight(char guess[])
{
	int pNum = 0;
	for(int i = 0; i < NUM_PEGS; i = i + 1)
	{
		if(guess[i] == secret[i])
			pNum = pNum + 1;
	}
	return pNum;
}

int MasterMind::numHalfRight(char guess[])
{
	int pNum = 0;
	bool check[NUM_PEGS];
	for(int i = 0; i < NUM_PEGS; i = i + 1)
	{
		if(guess[i] == secret[i])
			check[i] = false; 
		else
			check[i] = true;
	}

	for(int i = 0; i < NUM_PEGS; i = i + 1)
	{
		if(check[i] == true)
		{
			for(int j = 0; j < NUM_PEGS; j = j + 1)
			{
				if(check[j] == true && i != j)
					if(secret[j] == guess[i])
					pNum = pNum + 1;
			}
		}
	}
	return pNum;
}

bool MasterMind::isGoodGuess(char guess[])
{
	for(int i=0; i < NUM_PEGS; i = i+1)
	{
		
		if(guess[i] != 'B'||'b' && guess[i] != 'R'||'r' && guess[i] != 'G'||'g' && guess[i] != 'P'||'p' && guess[i] != 'Y'||'y')
			return false;
	}
	return true;
}