same hapened to me, I won the Espeon and it saved; whenever I went back to play it later for easy tokens, it said I had already chosen a pokemon, now it says that I am unable to participate.
I was replaying through my Emerald, and when I went to the second floor of the Devon Corp. HQ, there was a scientist who said that he was working on a machine that would make a visual representation of pokemon's dreams.
Whoa.