This bug was originally marked as duplicate of bug 175275, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.

Build: NetBeans IDE 6.9 RC2 (Build 201005312001)
VM: Java HotSpot(TM) Client VM, 16.3-b01, Java(TM) SE Runtime Environment, 1.6.0_20-b02
OS: Linux

User Comments:
gorrus: clicked on the arrow in diff

GUEST: Performing diff

giorgio42: once again...

giorgio42: Tried to copy a change from source to dest while diffiing.

GUEST: diffing files moving changes from two files.

argv: Was attempting to revert a single local change in a Subversion diff on a properties file. No other local changes are present in said file.

giorgio42: Still in 200911230200 (Cannot copy added stuff from left to right pane in Tools -> Diff to).

ronnystandtke: Clicking on an arrow in the middle of a diff view.

giorgio42: o Trying to copy lines from left to right window in diff (properties file).

GUEST: I was "diff"ing (Tools>Diff...) build.properties file with its last version. When I clicked on the arrow to insert the missing lines (shown in RED) in the target build.properties file from source build.properties file, this exception occured. The lines that were diffrent (shown in blue or green) were getting updated properly, by the arrow clicks. (Please note that 'Arrorw' is the symbol that appears in the column between the two side-by-side files in the diff-view.)

GUEST: I was using the mercurial status (base - locally modified)

nlloyd: Unable to diff properties file against properties file with .sample suffix

GUEST: diffing files with CVS diff editor

GUEST: I viewed the subersion changes of a file and tried to add a deleted line from the trunk with the arrow in the middle to the local file. However it did not work, but this exception was thrown.

yardus: Trying to apply change in the diff window

GUEST: Merging a file with conflicts

GUEST: Marcar a la flecha que copia un bloque de Base a Local en un dif de un archivo properties.

gholmer: Occurred while reverting a local change in Subversion.

adam_myatt: in a Subversion Diff window looking at changes in a file between two versions. clicked the red X icon to remove a green-highlighted addition to a file. error occurred.

georges: Trying to move some text from left to right in diff pane.

GUEST: manually merging a big .properties file

dcherk: in CVS diff window, moving a change from 'Base' to 'Locally Modified'




Stacktrace: 
java.beans.PropertyVetoException: Not allowed
   at org.openide.text.CloneableEditorSupport$Listener.vetoableChange(CloneableEditorSupport.java:2856)
   at org.netbeans.editor.BaseDocument.notifyModify(BaseDocument.java:1878)
   at org.netbeans.editor.BaseDocument.notifyModifyCheckStart(BaseDocument.java:1011)
   at org.netbeans.editor.BaseDocument.insertString(BaseDocument.java:751)
   at org.netbeans.modules.diff.builtin.visualizer.editable.EditableDiffView.rollback(EditableDiffView.java:687)
   at org.netbeans.modules.diff.builtin.visualizer.editable.LineNumbersActionsBar.performAction(LineNumbersActionsBar.java:203)