This server is running CraftBukkit version git-Bukkit-1.4.5-R0.2-36-g3b6f2a1-b2522jnks (MC: 1.4.5) (Implementing API version 1.4.5-R0.

10:55:48 [WARNING] [dynmap-mobs] Task #85 for dynmap-mobs v0.30 generated an exception
java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/entity/CraftEntity
at org.dynmap.mobs.DynmapMobsPlugin.updateMobs(DynmapMobsPlugin.java:180)
at org.dynmap.mobs.DynmapMobsPlugin.access$000(DynmapMobsPlugin.java:36)
at org.dynmap.mobs.DynmapMobsPlugin$MobUpdate.run(DynmapMobsPlugin.java:163)
at org.bukkit.craftbukkit.v1_4_5.scheduler.CraftTask.run(CraftTask.java:53)
at org.bukkit.craftbukkit.v1_4_5.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345)
at net.minecraft.server.v1_4_5.MinecraftServer.r(MinecraftServer.java:529)
at net.minecraft.server.v1_4_5.DedicatedServer.r(DedicatedServer.java:222)
at net.minecraft.server.v1_4_5.MinecraftServer.q(MinecraftServer.java:493)
at net.minecraft.server.v1_4_5.MinecraftServer.run(MinecraftServer.java:426)
at net.minecraft.server.v1_4_5.ThreadServerApplication.run(SourceFile:856)
Caused by: java.lang.ClassNotFoundException: org.bukkit.craftbukkit.entity.CraftEntity
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:34)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 10 more

Thanks that fixed it

Update to 0.40 - 0.30 didn't support 1.4.5, particularly after the recent arbitrary package changes....