pywin32+VirtualBox: guest VM crashes when trying to disable second monitor

Question

I wrote the following code to disable the a guest os's virtual monitor programatically:

def disableSecondMonitor():
    import win32api
    import win32con as C

    name = win32api.EnumDisplayDevices(None, 1).DeviceName
    devmode = win32api.EnumDisplaySettingsEx(name, 0)
    devmode.Clear()
    devmode.Fields = C.DM_PELSWIDTH | C.DM_PELSHEIGHT | C.DM_BITSPERPEL | \
                     C.DM_POSITION | C.DM_DISPLAYFREQUENCY | C.DM_DISPLAYFLAGS

    win32api.ChangeDisplaySettingsEx(name, devmode, C.CDS_UPDATEREGISTRY)
    win32api.ChangeDisplaySettingsEx(name, devmode, C.CDS_UPDATEREGISTRY)

The code is adapted from this article which says to make the API call twice with a zero-ed out devmode.

The strange thing is, the code works once in a while, but most often it causes the VM to restart. Any ideas?