This is in fact a bug in SuperLab that does not happen very often. We do have a few workarounds to hopefully get rid of the white box. The first one we suggest it Disable “Windows 7 Aero” (another name for this could be “Apply the Windows 7 Basic theme”).
Here are two relevant resources:
To stop getting the WHITE BOX during a running experiment, you should make sure no windows are open on your desktop.
Shutting down running applications can help the problem. However, the SuperLab window itself is a problem, and you can’t shut down SuperLab. If you have a windows folder open, you need to minimize or close it.
If you cannot shut things down, then minimize the windows.
We need to try and get the SuperLab window itself out of the way. You should move the SuperLab window down until it is almost off-screen, but still allowing you to hit the RUN button.
Please let me know which option worked for you.