I have a crash that happens when I use the invisibility for my unit. He can turn invisible just fine, but when I try and throw a grenade while he is invisible, it crashes. Any thoughts why? The grenade works just fine when he throws it and is visible.

Do you mean the Bothan Spy's invisible trick? Then maybe take a look at the timebomb odf's because the bothans can "throw" them still they're invisible.
I don't know but maybe there is a line that allows throwing stuff if you're invisible.