[SEVERE] Wrong location!

I had another drop of fps (very very annoying) so I choised to take a look at the console, and it shows this error:

Client> 2013-06-30 03:51:07 [SERVER] [SEVERE] Wrong location! tt['Zombie'/231609, l='Questo mondo survival è figo :3', x=-1118,50, y=29,00, z=-3724,50]
Client> java.lang.Exception: Stack trace
Client> 	at java.lang.Thread.dumpStack(Unknown Source)
Client> 	at adm.a(SourceFile:505)
Client> 	at abr.d(SourceFile:867)
Client> 	at acd.a(SourceFile:135)
Client> 	at jp.b(SourceFile:107)
Client> 	at net.minecraft.server.MinecraftServer.t(SourceFile:462)
Client> 	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
Client> 	at bko.s(SourceFile:124)
Client> 	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
Client> 	at hf.run(SourceFile:582)
Client> 2013-06-30 03:51:07 [SERVER] [SEVERE] Wrong location! tt['Zombie'/231609, l='Questo mondo survival è figo :3', x=-1118,50, y=29,00, z=-3724,50]
Client> java.lang.Exception: Stack trace
Client> 	at java.lang.Thread.dumpStack(Unknown Source)
Client> 	at adm.a(SourceFile:505)
Client> 	at abr.a(SourceFile:1374)
Client> 	at jp.a(SourceFile:480)
Client> 	at abr.g(SourceFile:1328)
Client> 	at abr.h(SourceFile:1235)
Client> 	at jp.h(SourceFile:364)
Client> 	at net.minecraft.server.MinecraftServer.t(SourceFile:470)
Client> 	at net.minecraft.server.MinecraftServer.s(SourceFile:405)
Client> 	at bko.s(SourceFile:124)
Client> 	at net.minecraft.server.MinecraftServer.run(SourceFile:339)
Client> 	at hf.run(SourceFile:582)