I am also having the same issue. I get this when it crashes
mrtjp/projectred/compatibility/CompatibilityCorePlugin : Unsupported major.minor version 51.0
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.lang.ClassLoader.defineClass1(Native Method)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.lang.ClassLoader.defineClass(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.security.SecureClassLoader.defineClass(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.net.URLClassLoader.defineClass(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.net.URLClassLoader.access$000(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.net.URLClassLoader$1.run(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.security.AccessController.doPrivileged(Native Method)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.net.URLClassLoader.findClass(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:113)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.lang.ClassLoader.loadClass(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.lang.ClassLoader.loadClass(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.lang.ClassLoader.loadClassInternal(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.lang.Class.forName0(Native Method)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at java.lang.Class.forName(Unknown Source)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.CoreModManager.loadCoreMod(CoreModManager.java:386)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.CoreModManager.discoverCoreMods(CoreModManager.java:310)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.CoreModManager.handleLaunch(CoreModManager.java:212)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLLaunchHandler.setupHome(FMLLaunchHandler.java:90)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLLaunchHandler.setupClient(FMLLaunchHandler.java:67)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLLaunchHandler.configureForClientLaunch(FMLLaunchHandler.java:34)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at cpw.mods.fml.common.launcher.FMLTweaker.injectIntoClassLoader(FMLTweaker.java:124)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at net.minecraft.launchwrapper.Launch.launch(Launch.java:111)
[b#431] 2014-03-08 11:19:15 [iNFO] [sTDERR] at net.minecraft.launchwrapper.Launch.main(Launch.java:27)
I am staff on a B-team server and need to be able to get on