The problem here appears to be that either currentAIstate was not constructed with new, or that you are sharing AI states between c_Zombie instances (so when you delete one c_Zombie's AI state, you are causing problems for other instances which were still using that AI state). Keep in mind that you should only use delete on objects constructed with new (so don't use delete on SDL_Surfaces)

The problem here appears to be that either currentAIstate was not constructed with new, or that you are sharing AI states between c_Zombie instances (so when you delete one c_Zombie's AI state, you are causing problems for other instances which were still using that AI state)