Mayavi window stop showing up

I've been using mayavi in python 3.5 and on a windows 10 machine. Today I was working on some script using mayavi and for no reason (that I know) the mayavi visualization window stopped showing up. In fact any mayavi example doesn't show the visualization window anymore. The scripts do wait on the mlab.show() but they won't show anything.

I've tried all the following but it still doesn't show the visualization window (each time just waiting at the mlab.show() command):

- Restart the machine and try again.
- pip install --upgrade for mayavi, vtk and pyQt4, then try again.
- I created a new virtualenv and install numpy, pyQt4, vtk, mayavi , then try again.
- I run the boy.py example with mlab.show(stop=True). The stop=True shows a window with a button "stop interaction" to finish the event loop. I see this window but not the visualization window. I thought maybe the window is there but hidden. I found WinLister which allows you to show all windows. I can see that the last opened windows are two QWidget, one is for the window with the close button and it shows as visible, and the other shows as not visible. I switch that window to visible and I see a window that could be the mayavi visualization window but it's all blank.
- If I step through the call to mlab.show() I see it eventually goes to the function start_event_loop_qt4() in site-packages/pyface/utils/guisupport.py and it waits indefinitely in the call to app.exec_(), nothing else happens.
- I've installed a new Python 3.5.2, create a new virtual environment and install numpy, pyQt4, vtk, mayavi , then try again, same problem.
- I went to another machine and install numpy, pyQt4, vtk, mayavi and the examples worked well (just checking I'm not going crazy).

Probably unrelated, but the last thing I was doing before the window stop showing up was recording a script from the mayavi properties window, I wanted to see what commands correspond to moving the viewpoint to a certain place. Once I saw the commands being recorded, I copied them and close the mayavi visualization window without stopping the recording. From that moment onwards I experienced the described problem.

Any idea what's going on?