I keep getting this in my console. I have no idea what causes it, nor do I know how to fix it. Code: 2013-02-10 18:52:42 [WARNING] Wrong location for EntityArrow['arrow'/429, l='hubworld', x=NaN, y=NaN, z=NaN] in world 'hubworld'! 2013-02-10 18:52:42 [WARNING] Entity is at NaN,NaN (chunk 0,0) but was stored in chunk 141,-3 2013-02-10 18:52:42 [WARNING] Wrong location for EntityArrow['arrow'/430, l='hubworld', x=NaN, y=NaN, z=NaN] in world 'hubworld'! 2013-02-10 18:52:42 [WARNING] Entity is at NaN,NaN (chunk 0,0) but was stored in chunk 141,-3 2013-02-10 18:52:42 [WARNING] Wrong location for EntityArrow['arrow'/431, l='hubworld', x=NaN, y=NaN, z=NaN] in world 'hubworld'! 2013-02-10 18:52:42 [WARNING] Entity is at NaN,NaN (chunk 0,0) but was stored in chunk 141,-3 2013-02-10 18:52:42 [WARNING] Wrong location for EntityArrow['arrow'/432, l='hubworld', x=NaN, y=NaN, z=NaN] in world 'hubworld'! 2013-02-10 18:52:42 [WARNING] Entity is at NaN,NaN (chunk 0,0) but was stored in chunk 141,-3 2013-02-10 18:52:42 [WARNING] Wrong location for EntityArrow['arrow'/433, l='hubworld', x=NaN, y=NaN, z=NaN] in world 'hubworld'! 2013-02-10 18:52:42 [WARNING] Entity is at NaN,NaN (chunk 0,0) but was stored in chunk 141,-3 Plugins: 20:20:56 [INFO] Plugins (37): TimTheEnchanter, LagMeter, bPermissions, WorldEdit, VoxelSniper, EssentialPads, TagAPI, CommandBook, PotionPermissions, Vault, Multiverse-Core, CombatTag, Grapple, Paintball, WorldGuard, bChatManager, HeroicDeathPlus, ChestRestock, HatMe, MagicSpells, SurvivalGames, CoreProtect, pvparena, ThrowDisks, PrettySigns, MicroJump, VariableTriggers, ScheduledAnnouncer2, FirstJoinPlus, mwParkour2, SuperSpleef, MobArena, Fe, rMessages, ServerSigns, NameTags, ecoCreature
Make sure to update each and everything on your server. This error message was common like quite a long time ago.