A glitch with fainted Pokemon?

Question

Sometimes when I' m battling the elite four in black 1 my games just goes weird.
Whenever I throw in a Pokemon and the other Pokemon uses an attack on me.
Instead of fainting it does this:

"pokemon name" fainted
then I choose the Pokemon I want to switch into.
But then this happens.
the HP bar just says 1/ "the full amount of HP of the previous Pokemon"
then when I choose an attack it says something (I forgot what exactly, but my Pokemon doesn't attack)
but then the enemy uses an attack and then the animation happens but the HP bar stays the same, so then I have to reset.
Any help?

Answer 1

In the link, skip to "Fainted Pokèmon Glitch".
http://bulbapedia.bulbagarden.net/wiki/List_of_glitches_in_Generation_V#Fainted_Pok.C3.A9mon_glitch
For convenience, here is what it says: Fainted Pokémon glitch
Sometimes in a battle a Pokémon will survive a would-be one-hit KO with one HP left, but will still faint. This occurs more often to low level Pokémon.
In a Single Battle, this prevents the player from switching out Pokémon or attack. The only way out of this is to reset the game.
In a Rotation Battle, the Pokémon can still be rotated out to a different Pokémon.-Bulbapedia