org.bukkit.command.PluginCommand.execute(PluginCommand.java:40)
07.02 19:12:59 [Server] INFO at org.kitteh.vanish.VanishCommand.onCommand(VanishCommand.java:43)
07.02 19:12:59 [Server] INFO at org.kitteh.vanish.VanishManager.toggleVanish(VanishManager.java:123)
07.02 19:12:59 [Server] INFO at org.kitteh.vanish.VanishManager.toggleVanishQuiet(VanishManager.java:174)
07.02 19:12:59 [Server] INFO Caused by: java.lang.NoSuchMethodError: org.bukkit.entity.Player.canSee(Lorg/bukkit/entity/Player;)Z
07.02 19:12:59 [Server] INFO at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)

Please help me ;)

You're running VNP 3.0, on a build earlier than 1871. Remember that 1.1-R3 is 1846.

Thanks :)