NoLagg Error

2012-11-21 12:44:01 [WARNING] [NoLagg] Task #10 for NoLagg v1.89.0 generated an
exception
java.lang.ClassCastException: net.minecraft.server.RegionFile cannot be cast to
java.lang.ref.Reference
        at com.bergerkiller.bukkit.nolagg.saving.RegionFileFlusher$1.run(RegionF
ileFlusher.java:30)
        at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:53)
        at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(C
raftScheduler.java:345)
        at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:529)
        at net.minecraft.server.DedicatedServer.r(DedicatedServer.java:222)
        at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:493)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:426)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:856)