I found the following exception in hudson.err.log:

9-dic-2009 12.33.01 hudson.model.Run run
INFO: Foundation #9 main build action completed: SUCCESS
9-dic-2009 12.33.03 hudson.plugins.analysis.core.BuildResult loadResult
INFO: Loaded data file C:\DeveloperTools\Hudson\jobs\Foundation\builds\2009-12-04_10-22-28\open-tasks.xml for build 7
9-dic-2009 12.33.05 hudson.plugins.analysis.core.BuildResult loadResult
INFO: Loaded data file C:\DeveloperTools\Hudson\jobs\Foundation\builds\2009-12-04_10-22-28\compiler-warnings.xml for build 7
9-dic-2009 12.33.07 hudson.model.Executor run
GRAVE: Executor throw an exception unexpectedly
java.lang.NoClassDefFoundError: hudson/plugins/tasks/util/model/Priority
at hudson.plugins.cigame.rules.plugins.opentasks.OpenTasksRuleSet.loadRules(OpenTasksRuleSet.java:14)
at hudson.plugins.cigame.rules.plugins.PluginRuleSet.getRules(PluginRuleSet.java:48)
at hudson.plugins.cigame.model.ScoreCard.record(ScoreCard.java:33)
at hudson.plugins.cigame.model.ScoreCard.record(ScoreCard.java:54)
at hudson.plugins.cigame.GamePublisher.perform(GamePublisher.java:56)
at hudson.plugins.cigame.GamePublisher.perform(GamePublisher.java:42)
at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:36)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:508)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:494)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:482)
at hudson.model.Build$RunnerImpl.cleanUp(Build.java:187)
at hudson.model.Run.run(Run.java:1216)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:123)
Caused by: java.lang.ClassNotFoundException: hudson.plugins.tasks.util.model.Priority
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
... 15 more