Re-installing Redpower error

[Guildy4]

im not sure if i am doing it right but when i try to reinstall redpower on my server (to try get rid of bugs) it will just give me the error message :

java.lang.NoClassDefFoundError: net/minecraft/server/mod_RedPowerMachine (wrong

name: mod_RedPowerMachine)

at java.lang.ClassLoader.defineClass1(Native Method)

at java.lang.ClassLoader.defineClassCond(Unknown Source)

at java.lang.ClassLoader.defineClass(Unknown Source)

at java.security.SecureClassLoader.defineClass(Unknown Source)

at java.net.URLClassLoader.defineClass(Unknown Source)

at java.net.URLClassLoader.access$000(Unknown Source)

at java.net.URLClassLoader$1.run(Unknown Source)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Unknown Source)

at cpw.mods.fml.common.Loader.loadModClass(Loader.java:440)

at cpw.mods.fml.common.Loader.attemptFileLoad(Loader.java:497)

at cpw.mods.fml.common.Loader.load(Loader.java:375)

at cpw.mods.fml.common.Loader.loadMods(Loader.java:527)

at cpw.mods.fml.server.FMLBukkitHandler.onPreLoad(FMLBukkitHandler.java:

113)

at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:118)

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:426)

at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)

as I said i'm not sure if i have installed this correctly but any help would be appreciated :)