Bug confirmed, thank you for reporting. The workaround is to simply change the view's zoom ratio (you can use the mouse wheel up and down for example). The problem only happens when a window has just been created; once you have changed the zoom everything is fine. Of course the bug is innocuous; it's just a screen rendering bug and has no effect on the image.
This is another Qt bug on Windows 8. It doesn't happen on all Windows 8 machines that we have tested, and seems hardware-dependent. Luckily it happens on the latest versions of VMware that we are using so we can reproduce it on our development virtual machines.
I'll try to fix this in the next version of PixInsight (less than a week now). Sorry for the inconvenience.
