Access Violation?

Hey guys, so I'm trying to write a program that will calculate all the primes in a number up to n using the Sieve of Eratostheneus algorithm. I've written the code, it compiles with no errors or warning. However, when I try to run it the program closes. After doing some debugging I found that the source of the problem is coming from a method call (i'll state which method later) and a message in Visual Studio 2012 pops up saying Access Violation. However, the method I'm calling is set to public so I don't really understand what's happening. Any guidance would be appreciated!

I believe the error is occuring within the int sieveEratosthenes(LList* p, int lstSize) function and it's specifically occuring at the node->setPrime(false); call.

//Class Declaration
class ListNode
{
friend class LList;

public:
	ListNode(int item = 0, bool pVal = false, ListNode* link=nullptr);
	int getItem() { return item_; }
	bool getPrime() { return prime_; }
	void setPrime(bool p) { prime_ = p; }
	ListNode* getNext() { return link_; }

private:
	int item_;
	bool prime_;
	ListNode *link_;
};

//function
int sieveEratosthenes(LList* p, int lstSize) 
{
	//locals
	ListNode* node;
	bool pTest = false;

	//Populate the List
	for(int j = 2; j < lstSize; j++) //Starts filling the list at 2
	{
		p->append(j, true); //Values are not considered prime until tested
		cout << j << " has been added to the list." << endl;
	}

	//Algorithm
	for(int i = 2; i < lstSize; i++)
	{
		node = p->_find(i - 2); //i - 2, sets position in list equal to value being evaluated
		pTest = node->getPrime();
		if(pTest) //if node value is prime
		{
			for(int j = 2 * i; j <= lstSize; j += i)
			{
				node = p->_find(j-2);
				node->setPrime(false);
			}
		}
	}

	return 0;
}