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This exception happens to me in a Maven project when visually styling on Android device. I experienced bug 228181 at the same time. org.netbeans.editor.GuardedException: Modification prohibited at org.netbeans.editor.BaseDocument.checkModifiable(BaseDocument.java:1046) at org.netbeans.editor.BaseDocument.remove(BaseDocument.java:926) at org.netbeans.modules.css.model.api.Model.applyChanges(Model.java:501) at org.netbeans.modules.css.model.api.Model.access$100(Model.java:95) at org.netbeans.modules.css.model.api.Model$3.run(Model.java:400) at org.netbeans.editor.GuardedDocument.runAtomicAsUser(GuardedDocument.java:347) at org.netbeans.modules.css.model.api.Model.applyChanges_AtomicLock(Model.java:396) at org.netbeans.modules.css.model.api.Model.applyChanges(Model.java:364) [catch] at org.netbeans.modules.css.visual.RuleEditorNode$1.run(RuleEditorNode.java:540) at org.netbeans.modules.css.model.api.Model$1.run(Model.java:273) at org.openide.util.Mutex.readAccess(Mutex.java:367) at org.netbeans.modules.css.model.api.Model.runReadTask(Model.java:270) at org.netbeans.modules.css.visual.RuleEditorNode.applyModelChanges(RuleEditorNode.java:536) at org.netbeans.modules.css.visual.RuleEditorNode$DeclarationProperty$2$1.run(RuleEditorNode.java:1097) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:727) at java.awt.EventQueue.access$200(EventQueue.java:103) at java.awt.EventQueue$3.run(EventQueue.java:688) at java.awt.EventQueue$3.run(EventQueue.java:686) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) at java.awt.EventQueue.dispatchEvent(EventQueue.java:697) at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138) at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
I think this happens if you are trying to modify read-only file, it seems like issue 225826
*** This bug has been marked as a duplicate of bug 225826 ***