CTooltipCtrl with custom paint causing SYSTEM CRASH!!!!!

Hi,

I have a CToolTipCtrl derived class which I am using to display text
as well as graphical data.

The tooltip class is handling the paint message in OnPaint() which
contains the text and drawing logic.

Following is a gist of the OnPaint():

///CODE START
CMyToolTip::OnPaint()
{

//CToolTipCtrl::OnPaint(); //if this is uncommented, below
drawing logic is not seen

if(someCondition)
{

                CPaintDC dc(this);

                CBrush br;
                brCreateSolidBrush(RGB(0, 0, 255));
                CBrush* pOldBrush = dc.SelectObject(&br);

                CFont font;
                font.CreatePointFont(90, _T("MS Shell Dlg"));
                CFont* pOldFont = dc.SelectObject(&font);

                CRect rc;
                GetWindowRect (&rc);
                //modify rect coordinates here
                MoveWindow (&rc); //resize the tooltip window

                //output some text
                CRect txtRc(rc);
                txtRc.right = l;
                SetTextWidth(&dc, txtRc, m_str); //m_str
contains text to be written
                dc.DrawText(m_str ,&txtRc, DT_LEFT);

                //do some drawing
                CRect someRect(somecoordinates,..);
                dc.Rectangle(&someRect)
                .
                .

                dc.SelectObject(pOldBrush);

                ::DeleteObject(dc.SelectObject(pOldFont));
                ::DeleteObject(pOldBrush);

                return;
}

CToolTipCtrl::OnPaint(); //have this too as above
drawing wont happen everytime

}
///CODE START

Now there is one object of CMyToolTip class in a view class. View
displays a geographical map and some objects on the map.
Hovering cursor over the objects should show tooltip. Some objects
have only text data and some have text and graphics data.

Problem is as follows:
Hovering mouse over text-only objects and text-graphics objects and
displaying their tooltips works fine, but continuously alternating
between the two after some time displays a blank tooltip or with wrong
data and eventually the whole system crashes!!! (windows blue scren)

The code has released GDI resources where required, so nt sure what
the problem is. Commenting the custom drawing part, does not
bring the crash. What seems to be wrong in the implementation? Please
help