I also have similiar problem like Clearest above..
When catching new pokemon, i usually using shiny & 100% catch rate AR codes..
I also use pokegen to change the pokemon nature too.
Every pokemon i catch can be stored to pc without problem but when i try to take the pokemon and put them in my party some of them will make my game error.
Now everytime i want to put that pokemon in party i always need to using pokegen.
Is the problem with my AR codes or because i change the nature?
I hope someone could help me since i dont know what i must do to fix this.
Here is my save file
Thanks in advance
XXXX - Pokemon White Version 2 (U) [Patched].SAV
