GroupManager Error

13:37:28 [SEVERE] tried to access class org.anjocaido.groupmanager.GroupManager$
1 from class org.anjocaido.groupmanager.GroupManager loading Permissions v2.5.1
(Is it up to date?)
java.lang.IllegalAccessError: tried to access class org.anjocaido.groupmanager.G
roupManager$1 from class org.anjocaido.groupmanager.GroupManager
        at org.anjocaido.groupmanager.GroupManager.enableScheduler(GroupManager.
java:106)
        at org.anjocaido.groupmanager.GroupManager.onEnable(GroupManager.java:83
)
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:118)
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader
.java:514)
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManage
r.java:216)
        at com.nijikokun.bukkit.Permissions.Permissions.onEnable(Permissions.jav
a:61)
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:118)
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader
.java:514)
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManage
r.java:216)
        at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:94)
        at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:72)
        at net.minecraft.server.MinecraftServer.e(MinecraftServer.java:215)
        at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:202)
        at net.minecraft.server.MinecraftServer.d(MinecraftServer.java:142)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:257)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:375)