What is there to do about this ... I love using the default theme but the calculator wont work ever since i upgraded to 4.0

When you say "default" theme, do you mean the 7730 small icons theme? If so, it just doesn't work. At this point there is nothing to do, other than going back to the theme supplied by the vendor for the 7100.

I "broke" my calculator by messing around with themes. Anyways it seems as if that certain combinations of themes will "break" it. To fix it, all I did was connect to to the DM, check the apps and discover that one of the themes I was using had caused a "downgrade" in the core applications. I allowed it to reinstall them and voila!

Does this make sense?

No.