actually it will only ice up on the inside if there is enough of a temp diff. from inside to outside and there is mositure on the inside. what happens is condestation then the condenstation freezes and you get ice. 2005gp the only reason you would have got that effect is if you used too much fog-x.
using fog-x is a way to help prevent it, but there is a trick to it. it can't be put on too heavily or too lightly, which is a major pain in the butt. i get it only once in a while, but i have just been living with it for now.