OK problem solved.
I had Vuze set to shutdown my PC once the download was complete. Before anyone gets upset about leechers who shutdown as soon as a download completes, the best upload speeds I can manage on my crappy ADSL connection is 10Kb/s, so it's not like I can really contribute much.
Anyway, I came home and the PC was off, so I assumed the download had completed, and went to install.
What had actually happened is that Vuze had downloaded and update ... and then shut down the PC!!!
So now I'm sitting at 1.8% and 2 days, 2 hours to go on the final release :(
Mods, please close this thread.
oh, and thanks for the suggestions guys, I appreciate the help.