Hibernate constraint violation when adding reviewers

2013-08-22 04:28:16,645 ERROR - Exception "org.hibernate.exception.ConstraintViolationException: could not insert: [com.cenqua.crucible.model.ReviewParticipant]" (javax.servlet.ServletException) while processing "/json/cru/CR-1/postDetails" (Referer:"https://acsfisheye.honeywell.com/cru/CR-1")
javax.servlet.ServletException: org.hibernate.exception.ConstraintViolationException: could not insert: [com.cenqua.crucible.model.ReviewParticipant]
	at com.opensymphony.webwork.dispatcher.DispatcherUtils.serviceAction(DispatcherUtils.java:284)
	at com.opensymphony.webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:111)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
	at org.mortbay.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1272)
	at com.atlassian.plugin.servlet.filter.IteratingFilterChain.doFilter(IteratingFilterChain.java:46)
	at com.atlassian.plugin.servlet.filter.DelegatingPluginFilter$1.doFilter(DelegatingPluginFilter.java:66)
	at com.atlassian.applinks.core.rest.context.ContextFilter.doFilter(ContextFilter.java:25)
…
Caused by: org.hibernate.exception.ConstraintViolationException: could not insert: [com.cenqua.crucible.model.ReviewParticipant]
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
	at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2438)
…
Caused by: java.sql.SQLException: Violation of UNIQUE KEY constraint 'UQ__cru_revi__5067DE081332DBDC'. Cannot insert duplicate key in object 'dbo.cru_review_participant'. The duplicate key value is (7983, 12).
	at net.sourceforge.jtds.jdbc.SQLDiagnostic.addDiagnostic(SQLDiagnostic.java:368)
	at net.sourceforge.jtds.jdbc.TdsCore.tdsErrorToken(TdsCore.java:2820)
	at net.sourceforge.jtds.jdbc.TdsCore.nextToken(TdsCore.java:2258)
	at net.sourceforge.jtds.jdbc.TdsCore.getMoreResults(TdsCore.java:632)