Hi James,
I think the file didn't download fully. When you first downloaded was the file in tact then?
You could you and use WinRAR to repair the file and it will potentially allow the files that are there to be extracted and just strip all the missing data out.
We are introducing a new feature to try mitigate this problem as some servers appear to mangle our response so the web browser doesn't know what size to expect and can't error if it doesn't get it all, which is of course an issue. This will hopefully be finished soon and will allow direct downloads that will work perfectly.
Jason