Weird Assertion Error.. HELP!

I have a program which creates has a thread which listens for socket connections. (ie a socket server.) The socket server spawns as many connections as needed... but that's not where my problem is. Say I merely start my program, then close it. My OnClose() then does this:

SSThread->PostThreadMessage(WM_QUIT, 0, 0);
WaitForSingleObject(SSThread->m_hThread, 2000);

Which should close the thread politely. I don't think that's the problem either! The problem is an assertion error I get EVERY time I close the program. It doesn't matter whether ANY sockets have been spawned from the socket server... so the problem must lie in the listening socket. The assertion error I get is:

Debug Assertion Failed!
Program: MyProgram.exe
File: sockcore.cpp
Line: 482

The line the above refers to is:

ASSERT(CAsyncSocket::LookupHandle(hSocket, FALSE) != NULL);

Well... here is the entire code for my socket server thread:

UINT StartSocketServer(LPVOID unused)
{
      CString                  temp;
      char                  eBuf[256];
      DWORD                  tid = GetCurrentThreadId();

      // create a socket
      if (!g_aSocket.Create(1079, SOCK_STREAM))  {
            sprintf(eBuf, "Thread %X: aSocket.Create failure %d",
                                                tid, GetLastError());
            AfxMessageBox(eBuf);
            return FALSE;
            }
      else  {
            sprintf(eBuf, "Thread %X: Socket created & bound on port 1079",tid);
            temp = eBuf;
            MainDlg->UpdateCommandStatus(temp += "\r\n");
            }

      // listen to the socket

      if (!g_aSocket.Listen())  {
            sprintf(eBuf, "Thread %X: g_aSocket.Listen failure %d",
                                                tid, GetLastError());
            AfxMessageBox(eBuf);
            }
      else  {
            sprintf(eBuf,"Thread %X: Socket listening on port 1079", tid);
            temp = eBuf;
            MainDlg->UpdateCommandStatus(temp += "\r\n");
            }

      // fall into a message loop

      MSG aMsg;

      while (GetMessage(&aMsg,NULL,NULL,NULL) > 0)  
      {
            switch(aMsg.message)
            {
                  case WM_QUIT:
                        break;
                  default:
                        TranslateMessage(&aMsg);
                        DispatchMessage(&aMsg);
            }
      }
return TRUE;
}

Note that g_aSocket is a global variable of type CMyAsyncSocket. Also note that while the program is running... it works great! What am I doing wrong to cause this assertion??? The only other place I do anything with winsock is my application classes constructor/destructor. Here is the code for both of those:


CMyApp::CMyApp()
{
      WORD wVersionRequested;
      WSADATA wsaData;
      int err;
 
      wVersionRequested = MAKEWORD(1, 1);
      err = WSAStartup(wVersionRequested, &wsaData);

      if (err != 0)
      {
            AfxMessageBox(IDS_WSAERROR);
          return;
      }

      if (LOBYTE(wsaData.wVersion) != 1 || HIBYTE(wsaData.wVersion) != 1)
      {
            AfxMessageBox(IDS_WSAERROR);
            WSACleanup();
            return;
      }
}

CMyApp::~CMyApp()
{
      WSACleanup();
}

HELP!!!