Bug 69240 [reconciling] Editor shows "stale" compilation error
Eclipse has always has a small problem in that occaisionally it would show an error in the editor window (red-squiggly, with a marker) even though the error had been fixed and no longer appeared in the Tasks/Problem view. I usually just type "Space-Backspace" and save the file and it goes away. In 3.0, this is MUCH more frequent. I'm not 100% sure of the cause, but every time I've seen in it recently, file A will have a problem, and then I'll change file B to fix it. I'll pay more attention, and see if I can obtain any more details.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/JavaReconciler.java
/*
	 * @see org.eclipse.jface.text.reconciler.IReconciler#install(org.eclipse.jface.text.ITextViewer)
	 */
	public void install(ITextViewer textViewer) {
		super.install(textViewer);
		
		fPartListener= new PartListener();
		IWorkbenchPartSite site= fTextEditor.getSite();
		IWorkbenchWindow window= site.getWorkbenchWindow();
		window.getPartService().addPartListener(fPartListener);
		
		fActivationListener= new ActivationListener(textViewer.getTextWidget());
		Shell shell= window.getShell();
		shell.addShellListener(fActivationListener);
		
		fJavaElementChangedListener= new ElementChangedListener();
		JavaCore.addElementChangedListener(fJavaElementChangedListener);
		
		fResourceChangeListener= new ResourceChangeListener();
		IWorkspace workspace= JavaPlugin.getWorkspace();
		workspace.addResourceChangeListener(fResourceChangeListener);
	}
	/*
	 * @see org.eclipse.jface.text.reconciler.IReconciler#uninstall()
	 */
	public void uninstall() {
		
		IWorkbenchPartSite site= fTextEditor.getSite();
		IWorkbenchWindow window= site.getWorkbenchWindow();