Scroller problems

I'm writing 'Windows' program in BP 7.0 and I have a problem.
When I open one window in my application everything works correct but in
case of opening second window the problem appears. The scroller in my one
window doesn't work correctly (X-scroller doesn't scroll all picture and
during scrolling the window is not refreshed so it looks like many the same
pictures drawn one close the other). Additionally picture is drawn at
absolute top left hand window corner so some part of the picture is on the
caption bar.
All trouble I have when I run my application on Windows 3.11. When I run it
on Windows 95 I don't have any problems.
Is there someone who know what is the reason of my problems?
Please help me.
Thanks in advance,