Bug 305375 [ui] Many dialogs about unavailable sites
I20100309-0100 I ran a "Check for Updates" immediately after my machine had come out of standby. I don't think the wireless had fully connected yet, and the check for updates failed (fine). However, I got a half dozen nested dialogs about each of the sites that it could not find. They were all stacked on top of one another, and I had to dismiss each one individually. I would expect it to accumulate this into a single dialog rather than one dialog per repository.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
public void forgetContribution(Object element) {
		contributionMemory.remove(element);
		contributionMemoryFirstClass.remove(element);
	}
	
	/**
	 * @param element
	 * @return the remembered NavigatorContentDescriptor
	 */
	public NavigatorContentDescriptor getContribution(Object element)
	{
		NavigatorContentDescriptor desc = (NavigatorContentDescriptor) contributionMemory.get(element);
		return desc;
	}
	
	/**
	 * 
	 * @param element
	 *            The element contributed by the descriptor to be returned
	 * @return The descriptor that contributed the element or null.
	 * @see #findContentExtensionsByTriggerPoint(Object)
	 */
	public synchronized NavigatorContentDescriptor getSourceOfContribution(Object element) {
		if (element == null)
			return null;
		if (structuredViewerManager == null)
			return null;
		
		NavigatorContentDescriptor src = (NavigatorContentDescriptor) contributionMemory.get(element);
		if (src != null)