A player died by a Wiether Skeleton in the Nether and the plugin (version 4.0.0.2488-Snapshot) threw a Java error and failed to perform. No chest was created and no colored death message.

Error: http://pastebin.com/rw1A9ugH
Config: http://pastebin.com/gVKSGXLZ

I am running Bukkit version 1.4.5_R02 (Beta) using the following plugins:
MineBackup, PickBoat, WorldEdit, Colors, simpleWeahter, PermissionsBukkit, ProteCoulissante, Message of the Day, Bedtime, WirelessRedstone, PlgRailBoost, Multiverse-Core, Multiverse-Portals, Multiverse-Inventories, LWC, WorldGuard, BiomeEdit, dynmap, Dynmap-Worldguard, WorldBorder, HomeSpawnPlus, DeathTpPlus

The plugin seems to work normally for pre-1.4 mobs as far as I can tell but this has not been fully validated.

Thanks for the bug report. I'll take a look.

Try this dev build.