Using version 2.3 of the ssh plugin, with jenkins versions 1.531 or 1.536, the plugin throws the below error and the user interface elements are missing on the job configuration page. Previous jobs that have been setup to use the plugin display a blank area with a 'delete' button. The plugin appears to work in jenkins version 1.408.3

Caused by: java.lang.AssertionError: class org.jvnet.hudson.plugins.SSHBuilder is missing its descriptor
at jenkins.model.Jenkins.getDescriptorOrDie(Jenkins.java:1179)
at hudson.tasks.Builder.getDescriptor(Builder.java:67)