Possible for non-unique author mappings to exist

2009-04-07 08:56:07,316 ERROR [btpool0-35] [AuthorHibernateDao] Problems getting author by name 
net.sf.hibernate.NonUniqueResultException: query did not return a unique result: 18
	at net.sf.hibernate.impl.AbstractQueryImpl.uniqueElement(AbstractQueryImpl.java:559)
	at net.sf.hibernate.impl.CriteriaImpl.uniqueResult(CriteriaImpl.java:385)
	at com.atlassian.bamboo.author.AuthorHibernateDao.getAuthorByName(AuthorHibernateDao.java:36)
	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:585)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
	at $Proxy2.getAuthorByName(Unknown Source)
	at com.atlassian.bamboo.author.HibernateAuthorManagerImpl.getAuthorByName(HibernateAuthorManagerImpl.java:51)
	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:585)