There was an update for MCForge I didn't know about.
Was working fine for 1.15, swapped the .jar in the mod folder and I get this error. Build Craft 2.2.3 seems to be working fine.
C:\minecraft>java -Xmx2048M -Xms2048M -jar minecraft_server.jar nogui
161 recipes
17 achievements
ModLoader Server Beta 1.8.1 Initializing...
2011-10-23 14:57:43 [INFO] ModLoader Server Beta 1.8.1 Initializing...
Mod Loaded: mod_BuildCraftCore 2.2.3
2011-10-23 14:57:43 [INFO] Mod Loaded: mod_BuildCraftCore 2.2.3
Mod Loaded: mod_BuildCraftBuilders 2.2.3
2011-10-23 14:57:43 [INFO] Mod Loaded: mod_BuildCraftBuilders 2.2.3
Mod Loaded: mod_BuildCraftEnergy 2.2.3
2011-10-23 14:57:43 [INFO] Mod Loaded: mod_BuildCraftEnergy 2.2.3
Mod Loaded: mod_BuildCraftFactory 2.2.3
2011-10-23 14:57:43 [INFO] Mod Loaded: mod_BuildCraftFactory 2.2.3
Mod Loaded: mod_BuildCraftTransport 2.2.3
2011-10-23 14:57:43 [INFO] Mod Loaded: mod_BuildCraftTransport 2.2.3
Failed to load mod from "mod_IC2.class"
java.lang.NoClassDefFoundError: forge/IOreHandler
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.privateGetPublicFields(Unknown Source)
at java.lang.Class.getFields(Unknown Source)
at ModLoader.setupProperties(ModLoader.java:133)
at ModLoader.addMod(ModLoader.java:103)
at ModLoader.readFromModFolder(ModLoader.java:847)
at ModLoader.init(ModLoader.java:603)
at ModLoader.Init(ModLoader.java:1269)
at net.minecraft.server.MinecraftServer.c(MinecraftServer.java:74)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:262)
at ce.run(SourceFile:417)
Caused by: java.lang.ClassNotFoundException: forge.IOreHandler
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)
... 12 more
Oct 23, 2011 2:57:43 PM ModLoader ThrowException
SEVERE: Unexpected exception
java.lang.NoClassDefFoundError: forge/IOreHandler
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.privateGetPublicFields(Unknown Source)
at java.lang.Class.getFields(Unknown Source)
at ModLoader.setupProperties(ModLoader.java:133)
at ModLoader.addMod(ModLoader.java:103)
at ModLoader.readFromModFolder(ModLoader.java:847)
at ModLoader.init(ModLoader.java:603)
at ModLoader.Init(ModLoader.java:1269)
at net.minecraft.server.MinecraftServer.c(MinecraftServer.java:74)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:262)
at ce.run(SourceFile:417)
Caused by: java.lang.ClassNotFoundException: forge.IOreHandler
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)
... 12 more
java.lang.RuntimeException: Exception occured in ModLoader
at ModLoader.ThrowException(ModLoader.java:1206)
at ModLoader.ThrowException(ModLoader.java:1211)
at ModLoader.addMod(ModLoader.java:118)
at ModLoader.readFromModFolder(ModLoader.java:847)
at ModLoader.init(ModLoader.java:603)
at ModLoader.Init(ModLoader.java:1269)
at net.minecraft.server.MinecraftServer.c(MinecraftServer.java:74)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:262)
at ce.run(SourceFile:417)
Caused by: java.lang.NoClassDefFoundError: forge/IOreHandler
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.privateGetPublicFields(Unknown Source)
at java.lang.Class.getFields(Unknown Source)
at ModLoader.setupProperties(ModLoader.java:133)
at ModLoader.addMod(ModLoader.java:103)
... 6 more
Caused by: java.lang.ClassNotFoundException: forge.IOreHandler
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)
... 12 more
Oct 23, 2011 2:57:43 PM ModLoader ThrowException
SEVERE: Unexpected exception
java.lang.RuntimeException: Exception occured in ModLoader
at ModLoader.ThrowException(ModLoader.java:1206)
at ModLoader.ThrowException(ModLoader.java:1211)
at ModLoader.addMod(ModLoader.java:118)
at ModLoader.readFromModFolder(ModLoader.java:847)
at ModLoader.init(ModLoader.java:603)
at ModLoader.Init(ModLoader.java:1269)
at net.minecraft.server.MinecraftServer.c(MinecraftServer.java:74)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:262)
at ce.run(SourceFile:417)
Caused by: java.lang.NoClassDefFoundError: forge/IOreHandler
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.privateGetPublicFields(Unknown Source)
at java.lang.Class.getFields(Unknown Source)
at ModLoader.setupProperties(ModLoader.java:133)
at ModLoader.addMod(ModLoader.java:103)
... 6 more
Caused by: java.lang.ClassNotFoundException: forge.IOreHandler
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)
... 12 more
java.lang.RuntimeException: ModLoader has failed to initialize.
at ModLoader.ThrowException(ModLoader.java:1206)
at ModLoader.init(ModLoader.java:627)
at ModLoader.Init(ModLoader.java:1269)
at net.minecraft.server.MinecraftServer.c(MinecraftServer.java:74)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:262)
at ce.run(SourceFile:417)
Caused by: java.lang.RuntimeException: Exception occured in ModLoader
at ModLoader.ThrowException(ModLoader.java:1206)
at ModLoader.ThrowException(ModLoader.java:1211)
at ModLoader.addMod(ModLoader.java:118)
at ModLoader.readFromModFolder(ModLoader.java:847)
at ModLoader.init(ModLoader.java:603)
... 4 more
Caused by: java.lang.NoClassDefFoundError: forge/IOreHandler
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.privateGetPublicFields(Unknown Source)
at java.lang.Class.getFields(Unknown Source)
at ModLoader.setupProperties(ModLoader.java:133)
at ModLoader.addMod(ModLoader.java:103)
... 6 more
Caused by: java.lang.ClassNotFoundException: forge.IOreHandler
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)
... 12 more
2011-10-23 14:57:43 [SEVERE] Unexpected exception
java.lang.RuntimeException: ModLoader has failed to initialize.
at ModLoader.ThrowException(ModLoader.java:1206)
at ModLoader.init(ModLoader.java:627)
at ModLoader.Init(ModLoader.java:1269)
at net.minecraft.server.MinecraftServer.c(MinecraftServer.java:74)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:262)
at ce.run(SourceFile:417)
Caused by: java.lang.RuntimeException: Exception occured in ModLoader
at ModLoader.ThrowException(ModLoader.java:1206)
at ModLoader.ThrowException(ModLoader.java:1211)
at ModLoader.addMod(ModLoader.java:118)
at ModLoader.readFromModFolder(ModLoader.java:847)
at ModLoader.init(ModLoader.java:603)
... 4 more
Caused by: java.lang.NoClassDefFoundError: forge/IOreHandler
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Unknown Source)
at java.lang.Class.privateGetPublicFields(Unknown Source)
at java.lang.Class.getFields(Unknown Source)
at ModLoader.setupProperties(ModLoader.java:133)
at ModLoader.addMod(ModLoader.java:103)
... 6 more
Caused by: java.lang.ClassNotFoundException: forge.IOreHandler
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)
... 12 more