GWT Encountered an Unexpected exception - gwt

Question

I am working on GWT application at the moment. I have imported the project onto my laptop since I was working on it on my desktop last night. However I am now getting this error.
Encountered a problem: Unexpected exception
Please see the logs [C:\Users----\AppData\Local\Temp\enhance7547571277273228846.log] for further information.
I also notice that my lib folder has a red marker over the icon which indicates a problem, it doesn't specify it though.
I did get this error once while working on my desktop last night and I managed to fix it by cleaning the project. When I try to clean the project now, I just get the same error.
Any ideas?
java.lang.RuntimeException: Unexpected exception
at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:76)
at com.google.appengine.tools.enhancer.Enhance.<init>(Enhance.java:71)
at com.google.appengine.tools.enhancer.Enhance.main(Enhance.java:51)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:74)
... 2 more
Caused by: org.datanucleus.exceptions.NucleusException: Plugin (Bundle) "org.datanucleus" is already registered. Ensure you dont have multiple JAR versions of the same plugin in the classpath.
The URL "file:/C:/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.4/appengine-java-sdk-1.7.4/lib/opt/tools/datanucleus/v2/datanucleus-core-3.1.1.jar" is already registered, and you are trying to register an identical plugin located at URL "file:/C:/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.4/appengine-java-sdk-1.7.4/lib/opt/user/datanucleus/v1/datanucleus-core-1.1.5.jar."
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:541)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:395)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensions(NonManagedPluginRegistry.java:219)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensionPoints(NonManagedPluginRegistry.java:160)
at org.datanucleus.plugin.PluginManager.<init>(PluginManager.java:65)
at org.datanucleus.plugin.PluginManager.createPluginManager(PluginManager.java:427)
at org.datanucleus.NucleusContext.<init>(NucleusContext.java:224)
at org.datanucleus.NucleusContext.<init>(NucleusContext.java:204)
at org.datanucleus.enhancer.DataNucleusEnhancer.<init>(DataNucleusEnhancer.java:160)
at org.datanucleus.enhancer.DataNucleusEnhancer.main(DataNucleusEnhancer.java:1133)
... 7 more
My Classpath
<?xml version="1.0" encoding="UTF-8"?>
<classpath>
<classpathentry kind="src" path="src"/>
<classpathentry kind="src" output="test-classes" path="test"/>
<classpathentry kind="con" path="com.google.appengine.eclipse.core.GAE_CONTAINER"/>
<classpathentry kind="con" path="com.google.gwt.eclipse.core.GWT_CONTAINER"/>
<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
<classpathentry exported="true" kind="lib" path="war/WEB-INF/lib/jsoup-1.7.2.jar"/>
<classpathentry kind="output" path="war/WEB-INF/classes"/>
</classpath>