Application crashes on BitBlt after a while.. need help please

Hello,

I call InvalidateRect() which calls OnPaint() which in turn calls a
function named DrawCompass().

The application works for a while... but then crashes. It leads me to
believe I have some memory leak or something not releasing resources
in time. The debugger says it crashes on the statement BitBlt.
Apparently it is unable to get a handle to something (i think the DC)
when using BitBlt and fails an ASSERT.

What am I doing wrong? Have I fogotten to delete some pointer in the
code below? Can you spot anything wrong with the code below?

Thank you for your time.

-----------------------------

void ScanDialog::OnPaint()
{
  CPaintDC dc(this);

  CDC dcMemory;
  bool falsetrue = dcMemory.CreateCompatibleDC (&dc);
  if(falsetrue == TRUE)
  {
    DrawCompass(IDC_AZIMUTH, &dcMemory);
  }
}

----------------------------

void ScanDialog::DrawCompass(int id, CDC * dcMemory)
{
  if(id == IDC_AZIMUTH)
  {
    pOldBitmap = dcMemory->SelectObject (&bmp); // pOldBitmap is a
CBitmap* pOldBitmap
    if(pOldBitmap != NULL)
    {
      pWndd = GetDlgItem(id);
      if(pWndd != NULL)
      {
        dc2 = pWndd->GetDC(); // dc is a CDC *dc2
   if(dc2 != NULL)
    {
          pWndd->GetClientRect(&rect); // rect is a CRect
          nX = rect.left;
          nY = rect.top;
          if(dc2->BitBlt(nX, nY, bmpInfo.bmWidth, bmpInfo.bmHeight,
dcMemory, 0, 0, SRCCOPY) != 0)
   {
            dc2->MoveTo(73,67);
            dc2->AngleArc(73,67,31,azimuth + 90,360); // azimuth is a
float
            dc2->MoveTo(73,67);
          }
    }
      }
      dcMemory->SelectObject(pOldBitmap);
    }
  }