I tried to use an X-Attack during battle, but selecting use on it kicked me back to the battle menu. My pokemon that was out was in the second slot of the party, so then I decided to experiment on random wild pokemon. I tried having the second slot out and using it on the first slot, same thing. I tried first slot out and using it on the first slot, same thing. Then I tried using it on every party slot without switching out, and still no difference. X items are just unusable.