Progress Bar border not being redrawn (Visual C++) - c++

Question

C++ in Visual Studio 2008 in Windows XP SP3
I have a CProgressCtrl on a dialog that is being updated in a loop that takes a while to complete. It starts hidden, goes visible for the loop, then hides again when complete.
Within the loop I call a doEvents() method that processes the message queue. This is ensuring that the form is redrawn when I move it, and that the progress bar boxes increase when I update the bar with SetPos()
The first time I use the progress bar it works fine. However, on subsequent uses, the bar appears without a border, and the border isn't being redrawn when the boxes increase (these are still drawn correctly).
How can I force the border of the progress bar to be (re)drawn? I've tried Invalidate(), UpdateWindow() & RedrawWindow() but none of them make a difference.
Interestingly, whilst the loop is running, if I drag the dialog off screen and back again, the border is immediately redrawn.
In case it is relevant, here's the doEvents() method I'm using (taken from here)
void MyClass::doEvents()
{
MSG msg;
BOOL result;
while ( ::PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE ) )
{
result = ::GetMessage(&msg, NULL, 0, 0);
if (result == 0) // WM_QUIT
{
::PostQuitMessage(msg.wParam);
break;
}
else if (result == -1)
{
// Handle errors/exit application, etc.
}
else
{
::TranslateMessage(&msg);
::DispatchMessage(&msg);
}
}
}