Multiple Viewports in Vizard, Utilizing keyboard callback

[shivanangel]

Thanks a lot.

I modified it slighty and kept it from crashing again.
I believe we are using an earlier version at our school.
A few decimal places behind the one you currently offer.

That probably accounts for the error. And since I was
adding a new viewport each time, I can see how it could
compound and create some problems after the 4th instance.

Thanks again,
George