After upgrading Jenkins from an older version to Jenkins 2.580:

• Jenkins starts successfully.
• When the Robot plugin is enabled, Jenkins pages become partially blank and all previous runs or results disappear.
• When the Robot plugin is disabled, all jobs and folders immediately reappear, but of course Robot functionality no longer works.
• Downgrading Jenkins to the previous version restores normal behavior without changing jobs, plugins, or data.

The exception is triggered while rendering Robot result columns in job views.

Error:
java.lang.ClassNotFoundException: org.apache.commons.lang.StringUtils
 
Caused by: java.lang.NoClassDefFoundError:
org/apache/commons/lang/StringUtils
 
at PluginClassLoader for robot//
hudson.plugins.robot.model.RobotCaseResult.getDuration(RobotCaseResult.java:121)
 
at PluginClassLoader for robot//
hudson.plugins.robot.model.RobotSuiteResult.tally(RobotSuiteResult.java:386)
 
at PluginClassLoader for robot//
hudson.plugins.robot.model.RobotResult.tally(RobotResult.java:386)
 
at PluginClassLoader for robot//
hudson.plugins.robot.RobotBuildAction.load(RobotBuildAction.java:184)
 
at PluginClassLoader for robot//
hudson.plugins.robot.RobotBuildAction.getResult(RobotBuildAction.java:150)
 
at PluginClassLoader for robot//
hudson.plugins.robot.view.RobotListViewColumn.getLastRobotResult(RobotListViewColumn.java:84)
 
at PluginClassLoader for robot//
hudson.plugins.robot.view.RobotListViewColumn.getTotal(RobotListViewColumn.java:34)