tooltips assert in tooltip.cpp line 383

When ever I position my mouse over a tool bar button of a debug build, an assert from tooltip.cpp line 383 is triggered.    The line referenced is the last line in the "if" block below.   Anyone know what is causing this?   I've tested this using a fresh "App Expert created project" and get the same results.

      if (!pToolTip->SendMessage(TTM_GETTOOLINFO, 0, (LPARAM)&ti))
            {
                  ASSERT(ti.cbSize == sizeof(TOOLINFO));
                  ASSERT(ti.uFlags == TTF_IDISHWND);
                  ASSERT(ti.hwnd == m_hWnd);
                  ASSERT(ti.uId == (UINT)m_hWnd);
                  VERIFY(pToolTip->SendMessage(TTM_ADDTOOL, 0, (LPARAM)&ti));
            }

I am using MSVC 5.0 (but I get the same results with version 4.2)    I've also recently reinstalled Windows 95 and MSVC 5.0.