After visualised a picture with "/vis/camera/viewpoint 0 0" set, if trying setting "/vis/camera/viewpoint 1 1" (or any positive angle), the resulting picture is flipped of 180 degrees (and probably also upside-down, could not verify this one...). BTW, in the problem reporting system, "G4Ray" component should be removed and be replaced by "RayTracer"...
Fix is committed to the CVS