IC2 Classic successfully triggers Railcraft's IC2 integration. However, IC2 Classic does not include the CESU, while Railcraft does have a CESU cart.

If the CESU cart is placed or spawned using creative mode, it causes a crash and will continue to crash any client which loads the chunk containing the cart.

@Nygmus jup i am ware of that and belive me you have either remove the Entity or reset the world... I have to write a Semi Railcraft fix for that and i do not have really much the time. Simply: It tries to render the CESU Item and it will crash because its not a block in IC2 Classic...

Railcraft/Railcraft#784 (comment)
@Nygmus update Railcraft as soon its getting its release