The 2.4.5 version of the TC plugin fails to load. Log from TC below. Reverting to 2.3.x version of the plugin resolves the issue for the time being.
[2014-05-14 20:09:20,303] ERROR - gins.spring.SpringPluginLoader - Failed to initialize spring context for plugin Octopus.TeamCity
org.springframework.beans.factory.CannotLoadBeanClassException: Error loading class [octopus.teamcity.server.OctopusBuildRunTypeExtension] for bean with name 'octopus.teamcity.server.OctopusBuildRunTypeExtension#0' defined in plugin: Octopus.TeamCity#Octopus.TeamCity.jar!/META-INF/build-server-plugin-Octopus.TeamCity.xml: problem with class file or dependent class; nested exception is java.lang.UnsupportedClassVersionError: octopus/teamcity/server/OctopusBuildRunTypeExtension : Unsupported major.minor version 52.0
at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1253)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:576)
at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1319)
at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:885)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:562)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
at jetbrains.buildServer.plugins.spring.SpringPluginLoader.pluginClassesLoaded(SpringPluginLoader.java:72)
at sun.reflect.GeneratedMethodAccessor60.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at jetbrains.buildServer.util.EventDispatcher.dispatch(EventDispatcher.java:117)
at jetbrains.buildServer.util.EventDispatcher$2.invoke(EventDispatcher.java:67)
at com.sun.proxy.$Proxy7.pluginClassesLoaded(Unknown Source)
at jetbrains.buildServer.plugins.PluginManagerImpl$2.visitPlugin(PluginManagerImpl.java:122)
at jetbrains.buildServer.plugins.PluginsCollection.foreachLoadedPlugins(PluginsCollection.java:107)
at jetbrains.buildServer.plugins.PluginManagerImpl.firePluginClassesLoaded(PluginManagerImpl.java:120)
at jetbrains.buildServer.plugins.PluginManagerImpl.loadPlugins(PluginManagerImpl.java:80)
at jetbrains.buildServer.web.plugins.PluginManagerConfigurator.initializePlugins(PluginManagerConfigurator.java:9)
at jetbrains.buildServer.web.impl.BuildServerConfigurator.loadConfiguration(BuildServerConfigurator.java:105)
at jetbrains.buildServer.maintenance.TeamCityDispatcherServlet$WebApplicationCreatorAndDestroyer.createApplication(TeamCityDispatcherServlet.java:0)
at jetbrains.buildServer.maintenance.StartupProcessor.doApplicationStarting(StartupProcessor.java:83)
at jetbrains.buildServer.maintenance.StartupProcessor.processConcreteStage(StartupProcessor.java:613)
at jetbrains.buildServer.maintenance.StartupProcessor.processConcreteStageSafe(StartupProcessor.java:486)
at jetbrains.buildServer.maintenance.StartupProcessor.processTeamCityLifecycle(StartupProcessor.java:448)
at jetbrains.buildServer.maintenance.StartupProcessor.access$000(StartupProcessor.java:450)
at jetbrains.buildServer.maintenance.StartupProcessor$1.run(StartupProcessor.java:1)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.UnsupportedClassVersionError: octopus/teamcity/server/OctopusBuildRunTypeExtension : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at jetbrains.buildServer.plugins.classLoaders.TeamCityClassLoader.doLoadClass(TeamCityClassLoader.java:71)
at jetbrains.buildServer.plugins.classLoaders.TeamCityClassLoader.loadClass(TeamCityClassLoader.java:40)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at org.springframework.util.ClassUtils.forName(ClassUtils.java:257)
at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:408)
at org.springframework.beans.factory.support.AbstractBeanFactory.doResolveBeanClass(AbstractBeanFactory.java:1271)
at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1242)
... 27 more