I paste valid YAML into the YAML editor and it chokes on it.

I am guessing the editor does not handle YAML block literals correctly:
http://en.wikipedia.org/wiki/YAML#Newlines_preserved

Here is the YAML content:

JFrame:
    title: frame.title
    content:
        - JPanel:
            content:
                - JBSeparator: {name: sepName, text: header.name}
                - JLabel: {name: fNameLabel, text: label.firstName}
                - JTextField: {name: fNameField, onFocus: onFirstNameFocus, onFocusLost: onFirstNameFocusLost}
                - JLabel: {name: lNameLabel, text: label.lastName}
                - JTextField: {name: lNameField, onKeyPressed: onLastNameKeyPressed, onKeyReleased: onLastNameKeyReleased}
                - JLabel: {name: titleLabel, text: label.title}
                - JTextField: {name: titleField, onKeyTyped: onTitleKeyTyped}
                - JLabel: {name: dfLabel, text: label.displayFormat}
                - JComboBox: {name: dfCombo}
                - JLabel: {name: nickLabel, text: label.nickname}
                - JTextField: {name: nickField}
                - JBSeparator: {name: sepList, text: header.list}
                - JLabel: {name: labelEmail, text: label.email}
                - JTextField: {name: fieldEmail}                
                - JList: {name: textArea}
                - JButton: {name: addButton, text: button.add, actionCommand: add}
                - JButton: {name: deleteButton, text: button.delete, actionCommand: delete}
                - JButton: {name: editButton, text: button.edit, onAction: edit}
                - JButton: {name: advancedButton, text: button.advanced, actionCommand: advanced}
                - JButton: {name: okButton, text: button.ok, onAction: save}
                - JButton: {name: cancelButton, text: button.cancel, onAction: cancel}
            layout: |
                [pref]       [grow,100px]              [grow]               [pref]             
                sepName+*              
                >fNameLabel  fNameField=1  >lNameLabel lNameField+2=1
                >titleLabel  titleField=1  >nickLabel  nickField+2=1
                >dfLabel     dfCombo+*
                sepList+*
                >labelEmail  fieldEmail+3                                    addButton+1+4=3      
                textArea+4+3                                                 editButton=3         [grow]
                                                                             deleteButton=3
                                                                             advancedButton=3                          
                                  
                >okButton+*=2,cancelButton=2