My version 1.4.3 is unable to start .?
What happens when you try?
Does it help to clear the Java cache?
http://www.java.com/en/download/help/plugin_cache.xmlWhen I looked at the clients 1.4.3 was still the official stable client .
Is 1.5.0 now the official client ?
Yes, 1.5.0 is the latest version so that's the version you get unless you have been using a version-specific link.