The vizinput dialogs create a blocking action which will halt rendering and events. If you want the user to make selections while the script runs normally you can use one of Vizard's other GUI libraries. Does this work for you?
Code:
import vizinfo
import viz
import vizshape
viz.go()
info = vizinfo.InfoPanel('Press n to toggle visibility of the ball')
dropdown = info.addLabelItem('blah',viz.addDropList())
dropdown.addItems(['fsdg','sd'])
theball = vizshape.addCircle(pos=[0,1.5,5])
vizact.onkeydown('n', theball.visible, viz.TOGGLE)