Bukkit

New at setting up my own server.  I am starting from scratch on an Ubuntu box.

What steps will reproduce the problem?
1.  I've downloaded the most recent Bukkit version.
2.  I downloaded the most recent version of SuperLog.
3.  I get an error on loading SuperLog, however, the server loads without it (ie, not stopping start-up).
4.  I tried to load the prior version as well, and it did not load.

What is the expected output? What do you see instead?
23:40:22 [INFO] Starting minecraft server version 1.2.5
23:40:22 [INFO] Loading properties
23:40:22 [INFO] Starting Minecraft server on *:25565
23:40:22 [INFO] This server is running CraftBukkit version git-Bukkit-1.2.5-R1.0-b2149jnks (MC: 1.2.5) (Implementing API version 1.2.5-R1.0)
23:40:24 [SEVERE] Could not load 'plugins/_1.0_SuperLog.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: org/bukkit/event/player/PlayerListener
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:148)
        at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:305)
        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:230)
        at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:207)
        at org.bukkit.craftbukkit.CraftServer.<init>(CraftServer.java:183)
        at net.minecraft.server.ServerConfigurationManager.<init>(ServerConfigurationManager.java:53)
        at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:156)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:422)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.lang.NoClassDefFoundError: org/bukkit/event/player/PlayerListener
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
        at com.thescreem.SuperLog.<init>(SuperLog.java:26)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:532)
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:144)
        ... 8 more
Caused by: java.lang.ClassNotFoundException: org.bukkit.event.player.PlayerListener
        at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
        ... 38 more

What version of the product are you using?
Loading SuperLog 2.4 (_1.0_SuperLog.jar)

Do you have an error log of what happened?
See above.

Please provide any additional information below.
Here are other jars that I have loaded into the server including the dates, just in case there is a conflict somewhere else.
-rw-rw-r-- 1 ec2-user ec2-user  19791 Dec 17 03:29 _1.0_SuperLog.jar
-rw-rw-r-- 1 ec2-user ec2-user 125597 Mar 17 14:04 ChestShop.jar
-rw-r--r-- 1 ec2-user ec2-user  20327 Mar  6 18:29 Colors.jar
-rw-rw-r-- 1 ec2-user ec2-user 664630 Mar 29 17:58 Essentials.jar
-rw-rw-r-- 1 ec2-user ec2-user  12691 Mar 29 17:58 EssentialsSpawn.jar
-rw-rw-r-- 1 ec2-user ec2-user 166222 Apr  2 00:32 iConomy.jar
-rw-rw-r-- 1 ec2-user ec2-user  54094 Mar 30 21:40 MobDisguise.jar
-rw-rw-r-- 1 ec2-user ec2-user 314604 Mar 30 19:24 ShowCaseStandalone.jar
-rw-rw-r-- 1 ec2-user ec2-user  13574 Apr  2 16:23 Spectate.jar
-rw-rw-r-- 1 ec2-user ec2-user 762724 Mar 31 09:30 WorldEdit.jar
-rw-rw-r-- 1 ec2-user ec2-user 267785 Apr  7 21:46 WorldGuard.jar
-rw-rw-r-- 1 ec2-user ec2-user  12792 Feb  6 11:21 XrayInformer.jar