I have been using Limewire for a couple of years now and have had great results. I have always used macs and DSL connections.
Recently, every time I try to download anything it will connect, start to download, and then "need more sources" or "waiting on busy host". It seemed to start happening at the same time a banner popped up to upgrade to a newer version of Limewire. I remember the same thing happening in the past and I upgraded and my downloading went back to normal. Should I upgrade, or is it something else? I am using a mac book pro with a wireless dsl connection and Limewire 4.12.6.

If it worked for you in the past then you might as well upgrade again. The latest version of Limewire seems to be a lot better with 'Need more sources'.