求循环链表答疑

今天是国庆节的第四天，早上起来写了一个关于循环链表的程序。单循环链表的结构如下：

下面是我写的具体的程序：

#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>

typedef struct node
{

	int data;
	struct node *pNext;
}NODE,*PNODE;

PNODE creat_List(PNODE);

void traverse_List(PNODE);

PNODE Clear_List(PNODE);


int main()
{
	PNODE Last = NULL;
	Last = creat_List(Last);

	traverse_List(Last);

	Last = Clear_List( Last);



	free(Last);
	Last = NULL;

	traverse_List(Last);
	return 0;
}

PNODE creat_List(PNODE Last)
{

	int len = 0;
	int val = 0;
	int i;
	Last = (PNODE)malloc(sizeof(NODE));
	if(NULL == Last)
	{
		printf("内存分配失败\n");
		exit(0);
	}

	Last->pNext = Last;

	printf("请输入创建元素的个数\n");
	scanf("%d",&len);
	
	for(i = 0;i < len;i++)
	{
	PNODE pNew = (PNODE)malloc(sizeof(NODE));
	printf("请输入第%d元素的值",i+1);
	scanf("%d",&val);

	pNew->data = val;

	pNew->pNext = Last->pNext;

	Last->pNext = pNew;
	

	Last =pNew;

	

	}

return Last;


}

void traverse_List(PNODE Last)
{

	PNODE p = Last->pNext->pNext;
	

	while(p != Last->pNext)
	{
	
		printf("%d",p->data);
		p = p->pNext;
	}

	printf("\n");


}

PNODE Clear_List(PNODE Last)
{
	PNODE q = Last->pNext->pNext;

	while(q != Last->pNext)
	{
		PNODE p = q->pNext;
		free(q);
		q = NULL;
		q = p;
		
	}

	q->pNext = q;
	Last = q;

	return Last;




}

程序在运行的时候却崩溃了。结果如下：

程序可以正常的遍历输出，但却不能clear链表，是什么原因？请高手指点啊。