Bukkit

What steps will reproduce the problem?
1.
2.
3.

What is the expected output? What do you see instead?

What version of the product are you using?

Do you have an error log of what happened?
2012-10-21 12:50:54 [INFO] [DeathTpPlus] A creeper tried to make love with SuperSockMonkey...mmm.
2012-10-21 12:51:23 [INFO] Connection reset
2012-10-21 12:51:23 [INFO] SuperSockMonkey lost connection: disconnect.quitting
2012-10-21 12:51:25 [INFO] SuperSockMonkey logged in with entity id 264711 at ([world] 379.00099444875644, 78.0, 386.63914988796415)
2012-10-21 12:55:15 [WARNING] [DeathTpPlus] Task #801368 for DeathTpPlus v3.9.16.2320 generated an exception
java.lang.NullPointerException
    at java.util.Hashtable.put(Unknown Source)
    at org.simiancage.DeathTpPlus.logs.DeathLocationsLogDTP.load(DeathLocationsLogDTP.java:64)
    at org.simiancage.DeathTpPlus.logs.DeathLocationsLogDTP.<init>(DeathLocationsLogDTP.java:52)
    at org.simiancage.DeathTpPlus.helpers.DynMapHelperDTP$DeathLocationLayer.getMarkers(DynMapHelperDTP.java:299)
    at org.simiancage.DeathTpPlus.helpers.DynMapHelperDTP$Layer.updateMarkerSet(DynMapHelperDTP.java:190)
    at org.simiancage.DeathTpPlus.helpers.DynMapHelperDTP.updateMarkers(DynMapHelperDTP.java:356)
    at org.simiancage.DeathTpPlus.helpers.DynMapHelperDTP.access$200(DynMapHelperDTP.java:37)
    at org.simiancage.DeathTpPlus.helpers.DynMapHelperDTP$MarkerUpdate.run(DynMapHelperDTP.java:338)
    at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:53)
    at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345)
    at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:510)
    at net.minecraft.server.DedicatedServer.q(DedicatedServer.java:213)
    at net.minecraft.server.MinecraftServer.p(MinecraftServer.java:474)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:406)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:539)

Please provide any additional information below.

there is a problem with your Deathlocation, probably a world you do not have anymore.

could you try the beta of 4.0.0. ? https://github.com/dredhorse/DeathTpPlus/raw/master/Resources/DeathTpPlus-4.0.0-SNAPSHOT.jar