Uncaught TypeError: Cannot call method 'unselectable' of null

[Mutaz]

I'm getting the following error and I don't know how to deal with it. It just freezes the editor and stops it from initialising!

Uncaught TypeError: Cannot call method 'unselectable' of null new (2):265 a new (2):265 (anonymous function) new (2):262 h new (1):20 CKEDITOR.event.CKEDITOR.event.fire new (1):22 CKEDITOR.editor.CKEDITOR.editor.fire new (1):23 CKEDITOR.event.CKEDITOR.event.fireOnce new (1):22 CKEDITOR.editor.CKEDITOR.editor.fireOnce new (1):23 (anonymous function) new (2):203 n new (2):184 CKEDITOR.scriptLoader.load new (2):184 (anonymous function) new (2):202 (anonymous function) new (2):191 (anonymous function) new (2):189 n new (2):184 CKEDITOR.scriptLoader.load new (2):184 CKEDITOR.resourceManager.load new (2):188 g new (2):190 (anonymous function) new (2):191 h new (2):201 (anonymous function) new (2):200 CKEDITOR.lang.load new (2):182 k new (2):199 (anonymous function) new (2):199 a new (2):385 CKEDITOR.skin.loadPart new (2):387 g new (2):199 (anonymous function) new (2):199 h new (1):20 CKEDITOR.event.CKEDITOR.event.fire new (1):22 CKEDITOR.editor.CKEDITOR.editor.fire new (1):23 CKEDITOR.event.CKEDITOR.event.fireOnce new (1):22 CKEDITOR.editor.CKEDITOR.editor.fireOnce new (1):23 d new (2):199 (anonymous function) new (2):196 (anonymous function)