I lost a job that used the repo plugin, after restarting Jenkins. I checked the jenkins log, and this is the error shown in the log:
Jan 18, 2012 4:43:28 PM jenkins.InitReactorRunner$1 onTaskFailed
SEVERE: Failed Loading job Manifest_Monitor
java.lang.NullPointerException
at hudson.plugins.repo.RevisionState.hashCode(RevisionState.java:139)
at java.lang.Object.toString(Object.java:219)
at java.lang.String.valueOf(String.java:2826)
at java.util.Arrays.toString(Arrays.java:4071)
at java.util.concurrent.CopyOnWriteArrayList.toString(CopyOnWriteArrayList.java:860)
at java.lang.String.valueOf(String.java:2826)
at java.lang.StringBuilder.append(StringBuilder.java:115)
at org.jvnet.hudson.plugins.DownStreamProjectActionFactory.createFor(DownStreamProjectActionFactory.java:69)
at hudson.model.AbstractProject.createTransientActions(AbstractProject.java:612)
at hudson.model.Project.createTransientActions(Project.java:203)
at hudson.model.AbstractProject.updateTransientActions(AbstractProject.java:602)
at hudson.model.AbstractProject.onLoad(AbstractProject.java:272)
at hudson.model.Project.onLoad(Project.java:88)
at hudson.model.Items.load(Items.java:115)
at jenkins.model.Jenkins$14.run(Jenkins.java:2372)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at jenkins.model.Jenkins$5.runTask(Jenkins.java:812)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Jan 18, 2012 4:43:28 PM
org.jvnet.hudson.plugins.DownStreamProjectActionFactory createFor