I get this error on startup in latest Craftbukkit git-Bukkit-0.0.0-1131

20:16:46 [SEVERE] Could not load 'plugins\Multiverse-SignPortals.jar' in folder
'plugins':
java.lang.NoClassDefFoundError: com/onarandombox/MultiverseCore/api/MVPlugin
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14
2)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:36)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:24)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.j
ava:170)
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.
java:215)
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager
.java:136)
at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:136)
at org.bukkit.craftbukkit.CraftServer.(CraftServer.java:112)
at net.minecraft.server.ServerConfigurationManager.(ServerConfigur
ationManager.java:52)
at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:136)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:348)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:417)
Caused by: java.lang.ClassNotFoundException: com.onarandombox.MultiverseCore.api
.MVPlugin
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:36)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:24)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
... 24 more

Your Multiverse-Core is outdated. Update it.