Opengl rendering as control on child window of MDI App. in MFC

I have MFC MDI Application , where I create opengl window as derived class of CWnd. This class I use as a control on the CFormViews and render.
Problem I am having is, when the child formview is moved outside the monitor( invisible part of the desktop) and if i resize the child window in that position then whatever part of the opengl window is ourside the desktop(which is on that form view) doesn’t get rendered and leaves black patch when I move child window back inside the visible desktop area. Once I move back in and then if I redraw opengl (by resizing again) then black patch gets rendered and everything is normal.
I remember MS admitted the bug in generic implementation of win 2000 GL drivers where we saw two black patches right and bottom strips if no hardware acclearation.
But this one I am not sure what the heck is going on. Seems like Opengl doesn’t render when its outside the desktop.
most of the opengl application i have scene are glut windows or on the mfc dialogs or mfc CViews.
What I have is the one on CFormview.
Can anyone help?