syncronization

when when I run the VirtualScreen.cpp code, it will crash like this
(screen shot captured)

http://www.oniva.com/upload/1356/crash.jpg

it is something related to pointers which i am no familiar with.

Basically,
1) RFIDSock Class - i defined a key value pair - ID / timestamp, then
I insert the key value pair into a queue.

2) VirtualScreen Class - I have a reference to RFIDSock object
(pointer) and I am accessing RFIDSock's "queue" object (*IDs) and pop
any object the timestamp is old enough.

since both RFIDSock / VirtualScreen Class - both function is keep
calling every seconds or miliseconds.

RFIDSock - is inserting to the queue
VirtualScreen - is removing element from the queue

will there be some syncrohization problem for both function accessing
the queue every mililseconds / seconds?

I am very messed up in pointers, is the crash related to just simple
mistake in pointers?

=====================
RFIDSock.h
=====================
#include <map>
#include <list>
#include <string>
#include <queue>
#include "VirtualScreen.h"

typedef const char* id_type;
typedef unsigned int timestamp_type;
typedef std::pair<id_type, timestamp_type> entry_type;

//class CVirtualScreen;
class CVirtualScreen;

class RFIDSock
{
public:
    std::queue< entry_type > *IDs;

};

=====================
RFIDSock.cpp
=====================
#include "RFIDSock.h"
#include <queue>
#include <time.h>

class CVirtualScreen;

//--------------------------------------------------------------
void RFIDSock::OnDataReceived(const LPBYTE lpBuffer, DWORD dwCount)
{
    entry_type entry;
    entry.first = (const char*)m_bReceiveBuffer;
    entry.second = seconds;

    IDs->push( entry );

}
=====================
VirtualScreen.h
=====================
    RFIDSock *rfidsock;

=====================
VirtualScreen.cpp
=====================
void VirtualScreen::ProcessMessages()
{
    unsigned int current = time (NULL);
    while ( current - rfidsock->IDs->front().second > duration){
        rfidsock->IDs->pop();
    }
}