The error in your log file seems to indicate that it did not successfully download the file "Clearcore2.RawXYProcessing.dll".
There is nothing particular special about that file, so I think what happened was that there was a random network error and that if you were to try to install again, it would either succeed, or you would get a similar error on a different file.

What sort of error did you get when you tried to use the "unplugged" installer? I suspect that the error you got with the unplugged installer was completely different.
I think that your computer might be having network troubles and that if you try installing more times, it will probably eventually succeed.
Also, I believe that every time this fails, you are getting a slightly different error. If you could post the log files from your other failed attempts, we might be able to come up with a better theory about what is going wrong.
-- Nick