My players have reported several orphan fields that stayed even after removing their protection block. Running "/ps clean <world" did not find them. It just said "No orphans found"

I'm using your dev version: #154 (Dec 19, 2012 1:15:36 PM)
with CB 1.4.6-R0.1

I just tried Build #175 that said was supposed to fix "/ps clean "... When I run that command, I get:

2013-01-04 22:52:08 [INFO] Error: Cannot drop AIR.
2013-01-04 22:52:08 [INFO] org.apache.commons.lang.Validate.isTrue(Validate.java:157)
2013-01-04 22:52:08 [INFO] org.bukkit.craftbukkit.v1_4_6.CraftWorld.dropItem(CraftWorld.java:285)
2013-01-04 22:52:08 [INFO] org.bukkit.craftbukkit.v1_4_6.CraftWorld.dropItemNaturally(CraftWorld.java:302)
2013-01-04 22:52:08 [INFO] net.sacredlabyrinth.Phaed.PreciousStones.managers.ForceFieldManager.dropBlock(ForceFieldManager.java:2376)
2013-01-04 22:52:08 [INFO] net.sacredlabyrinth.Phaed.PreciousStones.managers.ForceFieldManager.dropBlock(ForceFieldManager.java:2320)
2013-01-04 22:52:08 [INFO] net.sacredlabyrinth.Phaed.PreciousStones.managers.ForceFieldManager.flush(ForceFieldManager.java:2309)
2013-01-04 22:52:08 [INFO] net.sacredlabyrinth.Phaed.PreciousStones.managers.ForceFieldManager.cleanOrphans(ForceFieldManager.java:761)
2013-01-04 22:52:08 [INFO] net.sacredlabyrinth.Phaed.PreciousStones.managers.CommandManager.onCommand(CommandManager.java:1725)
2013-01-04 22:52:08 [INFO] org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
2013-01-04 22:52:08 [INFO] org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:186)
2013-01-04 22:52:08 [INFO] org.bukkit.craftbukkit.v1_4_6.CraftServer.dispatchCommand(CraftServer.java:510)
2013-01-04 22:52:08 [INFO] org.bukkit.craftbukkit.v1_4_6.CraftServer.dispatchServerCommand(CraftServer.java:502)
2013-01-04 22:52:08 [INFO] net.minecraft.server.v1_4_6.DedicatedServer.al(DedicatedServer.java:260)
2013-01-04 22:52:08 [INFO] net.minecraft.server.v1_4_6.DedicatedServer.r(DedicatedServer.java:225)
2013-01-04 22:52:08 [INFO] net.minecraft.server.v1_4_6.MinecraftServer.q(MinecraftServer.java:494)
2013-01-04 22:52:08 [INFO] net.minecraft.server.v1_4_6.MinecraftServer.run(MinecraftServer.java:427)
2013-01-04 22:52:08 [INFO] net.minecraft.server.v1_4_6.ThreadServerApplication.run(SourceFile:849)
2013-01-04 22:52:08 [INFO] Command not recognized�[m