iOS/Xcode CI build is breaking - not completing

I'm getting this log output:

Failed to execute the build 'HELLOWORLD-HELLOWORLDBUILD-JOB1-2'
java.lang.NoClassDefFoundError: com/atlassian/bamboo/task/CommonTaskContext
        at java.lang.Class.getDeclaredConstructors0(Native Method)
        at java.lang.Class.privateGetDeclaredConstructors(Class.java:2398)
        at java.lang.Class.getConstructors(Class.java:1461)
        at org.springframework.beans.factory.support.AbstractBeanDefinition.getResolvedAutowireMode(AbstractBeanDefinition.java:520)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:832)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:440)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
        at java.security.AccessController.doPrivileged(Native Method)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:300)
        at sun.reflect.GeneratedMethodAccessor104.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at com.atlassian.plugin.osgi.spring.DefaultSpringContainerAccessor.createBean(DefaultSpringContainerAccessor.java:109)
        at com.atlassian.plugin.module.ClassPrefixModuleFactory.createModule(ClassPrefixModuleFactory.java:32)
        at com.atlassian.plugin.module.PrefixDelegatingModuleFactory.createModule(PrefixDelegatingModuleFactory.java:99)
        at com.atlassian.bamboo.plugin.descriptor.AbstractBambooModuleDescriptor.createModule(AbstractBambooModuleDescriptor.java:26)
        at com.atlassian.bamboo.plugin.descriptor.AbstractBambooModuleDescriptor.getModule(AbstractBambooModuleDescriptor.java:90)
        at com.atlassian.bamboo.task.TaskExecutorImpl.executeTasks(TaskExecutorImpl.java:183)
        at com.atlassian.bamboo.task.TaskExecutorImpl.execute(TaskExecutorImpl.java:94)
        at com.atlassian.bamboo.build.pipeline.tasks.ExecuteBuildTask.call(ExecuteBuildTask.java:87)
        at com.atlassian.bamboo.v2.build.agent.DefaultBuildAgent.build(DefaultBuildAgent.java:206)
        at com.atlassian.bamboo.v2.build.agent.BuildAgentControllerImpl.waitAndPerformBuild(BuildAgentControllerImpl.java:103)
        at com.atlassian.bamboo.v2.build.agent.DefaultBuildAgent$1.run(DefaultBuildAgent.java:111)
        at com.atlassian.bamboo.build.pipeline.concurrent.NamedThreadFactory$2.run(NamedThreadFactory.java:52)
        at java.lang.Thread.run(Thread.java:680)
Caused by: java.lang.ClassNotFoundException: com.atlassian.bamboo.task.CommonTaskContext
        at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
        at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:424)
        at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:377)
        at org.apache.felix.framework.ExtensionManager$ExtensionManagerModule.getClassByDelegation(ExtensionManager.java:672)
        at org.apache.felix.framework.resolver.WireImpl.getClass(WireImpl.java:99)
        at org.apache.felix.framework.ModuleImpl.searchImports(ModuleImpl.java:1345)
        at org.apache.felix.framework.ModuleImpl.findClassOrResourceByDelegation(ModuleImpl.java:711)
        at org.apache.felix.framework.ModuleImpl.access$200(ModuleImpl.java:73)
        at org.apache.felix.framework.ModuleImpl$ModuleClassLoader.loadClass(ModuleImpl.java:1690)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
        ... 26 more

When trying to run an Xcode/iOS build. According to the log it seems to be working fine, until it gets to the Maven stuff (we're not using maven)

16-May-2013 15:15:33	Updated source code to revision: b4ce29ec5b099488339169afc00aa8cd43f95b71
16-May-2013 15:15:33	Finished task 'Checkout Default Repository'
16-May-2013 15:15:33	Running pre-build action: Build Number Stamper
16-May-2013 15:15:33	Running pre-build action: Clover Grails PreBuild Action
16-May-2013 15:15:33	Running pre-build action: VCS Version Collector
16-May-2013 15:15:33	Running pre-build action: Repository Isolation Enabler Action
16-May-2013 15:15:33	Running pre-build action: Maven Settings Prebuild Action
16-May-2013 15:15:33	Failed to execute the build 'HELLOWORLD-HELLOWORLDBUILD-JOB1-2': com/atlassian/bamboo/task/CommonTaskContext

Any reason for this. I'm using the "Bamboo iOS, Cocoa and Xcode Support" plugin.