Main question: Are you seeing a "General Installation Error" at 50% of the install?
No, The progress bar shows that initialization goes to completion, then a new screen says that installation failed. Try again is an option, but with same results. I followed your multi-step procedure, but I had no previous Flash Player components on my machine.
1. Try creating a new (admin) account and see if it'll install under that account. This will be an indicator of premissions problems under your account if it works.
2. Las ditch effort - Install from Terminal per instructions here: http://forums.adobe.com/message/5059595