Just tested Vault v1.2.11-b130 with official R5 release. When enabling server, the following exception is thrown:

12:27:20 [SCHWERWIEGEND] Error occurred while enabling Vault v1.2.11-b130 (Is it up to date?)
java.lang.NoClassDefFoundError: org/bukkit/util/config/ConfigurationNode
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at net.milkbowl.vault.Vault.packageExists(Vault.java:504)
at net.milkbowl.vault.Vault.loadPermission(Vault.java:343)
at net.milkbowl.vault.Vault.onEnable(Vault.java:107)
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:215)
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:336)
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:363)
at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:249)
at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:231)
at org.bukkit.craftbukkit.CraftServer.(CraftServer.java:183)
at net.minecraft.server.ServerConfigurationManager.(ServerConfigurationManager.java:53)
at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:147)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:407)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)
Caused by: java.lang.ClassNotFoundException: org.bukkit.util.config.ConfigurationNode
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
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:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 15 more

Vault doesn't use old configuraion, it checks packages on load. This means you have another plugin that still tries to use the old configuration, probably iCo5 or P3.

Ah, ok - sorry to bother you.