Tried replacing 0.7 with 0.8 using the macos tgz version. Nothing changed, no hackery on our side in build details, got this fatal exception:

2006-12-20 10:25:08,977 INFO [main] [UpgradeTask120] Upgrading dependent build CAT-CPA
2006-12-20 10:25:09,038 ERROR [main] [UpgradeManagerImpl] org.springframework.orm.hibernate.HibernateSystemException: a different object with the same identifier value was already associated with the session: 229378, of class: com.atlassian.bamboo.build.DefaultBuild; nested exception is net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 229378, of class: com.atlassian.bamboo.build.DefaultBuild
org.springframework.orm.hibernate.HibernateSystemException: a different object with the same identifier value was already associated with the session: 229378, of class: com.atlassian.bamboo.build.DefaultBuild; nested exception is net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 229378, of class: com.atlassian.bamboo.build.DefaultBuild
net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 229378, of class: com.atlassian.bamboo.build.DefaultBuild
at net.sf.hibernate.impl.SessionImpl.checkUniqueness(SessionImpl.java:1687)
at net.sf.hibernate.impl.SessionImpl.doUpdateMutable(SessionImpl.java:1453)
at net.sf.hibernate.impl.SessionImpl.doUpdate(SessionImpl.java:1480)
at net.sf.hibernate.impl.SessionImpl.update(SessionImpl.java:1365)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.springframework.orm.hibernate.HibernateTemplate$CloseSuppressingInvocationHandler.invoke(HibernateTemplate.java:1111)
at $Proxy20.update(Unknown Source)
at com.atlassian.bamboo.build.BuildHibernateDao$5.doInHibernate(BuildHibernateDao.java:178)
at org.springframework.orm.hibernate.HibernateTemplate.execute(HibernateTemplate.java:364)
at org.springframework.orm.hibernate.HibernateTemplate.execute(HibernateTemplate.java:333)
at com.atlassian.bamboo.build.BuildHibernateDao.addChildBuild(BuildHibernateDao.java:174)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:287)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:181)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:148)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:170)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:176)
at $Proxy1.addChildBuild(Unknown Source)
at com.atlassian.bamboo.build.HibernateBuildManager.addChildBuild(HibernateBuildManager.java:250)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:287)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:181)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:148)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:170)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:176)
at $Proxy7.addChildBuild(Unknown Source)
at com.atlassian.bamboo.upgrade.tasks.UpgradeTask120.doUpgrade(UpgradeTask120.java:61)
at com.atlassian.bamboo.upgrade.UpgradeManagerImpl.doUpgrade(UpgradeManagerImpl.java:65)
at com.atlassian.bamboo.upgrade.UpgradeLauncher.contextInitialized(UpgradeLauncher.java:51)
at org.mortbay.jetty.servlet.WebApplicationContext.doStart(WebApplicationContext.java:497)
at org.mortbay.jetty.plus.PlusWebAppContext.doStart(PlusWebAppContext.java:149)
at org.mortbay.util.Container.start(Container.java:72)
at org.mortbay.http.HttpServer.doStart(HttpServer.java:753)
at org.mortbay.jetty.plus.Server.doStart(Server.java:153)
at org.mortbay.util.Container.start(Container.java:72)
at com.atlassian.bamboo.server.Server.main(Server.java:35)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at com.exe4j.runtime.LauncherEngine.launch(Unknown Source)
at com.install4j.runtime.Launcher.main(Unknown Source)

Don't know how. There's no redundant processes I can see hanging about on the linux box. Will keep looking in case it's something on my side