Bug 137073 [Preferences] Encoding field editor never fires value change events
The class AbstractEncodingFieldEditor never fires VALUE property change events unless the validaty of the value has also changed. I will attach a patch that corrects the problem.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/dialogs/AbstractEncodingFieldEditor.java
* (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.preference.FieldEditor#doLoad()
	 */
	protected void doLoad() {
		if (encodingCombo != null) {
			List encodings = IDEEncoding.getIDEEncodings();
			String resourcePreference = getStoredValue();
			populateEncodingsCombo(encodings, resourcePreference);
			updateEncodingState(resourcePreference == null);
		}
	}
	/**
	 * Returns the value that is currently stored for the encoding.
	 * 
	 * @return the currently stored encoding
	 */
	protected abstract String getStoredValue();
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.preference.FieldEditor#doLoadDefault()
	 */
	protected void doLoadDefault() {
		updateEncodingState(true);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.preference.FieldEditor#getNumberOfControls()