Lets see where do I start?
I have tried to install Adobe Flash 10.1.102.64 at least a half dozen times to use with IE8.
Both Darician, and roncerrs links point to the same programs.
I was sure to use my Administrator rights every time I went to install.
Yes, every new try included using the un-installer with a restart before I went on to install the ActiveX control, and then the actual Flash Program.
At first I only restarted after the un-installer, then I tried restarting after installing the other two, no difference.
I tried following the above procedures in safe mode, no difference.
I tried shutting down any anti-virus, malware, spyware, firewalls, clouds, no difference.
I tried resetting IE8 back to defaults, no difference.
I tried to install from different sites that required it, no difference.
I have tried installing an older version of Flash to see if I could get it to up date, no success.
I tried searching for kill-bits as suggested in this thread, but I did not have what the OP had listed or could not interpret the clsid
numbers. : Adobe Forums: Shockwave Flash Object not present as...
Different links I've been to: Adobe Forums: Adobe flash player will not install on...
Tried this, but it really doesn't apply to me: Adobe Forums: Flash Player 10.1 problem
I never got my versions of IE8 (x32) mixed with x64: Adobe Forums: flash player installs but doesn't work
I don't have this problem because I can't get it installed in the first place: Adobe Forums: Why do I have to install Flash Player...
General issues on the Flash Forum: Adobe Forums: Forum: Flash Player
I tried Troubleshooting the installation, and that means step by step by step by step to the end, didn't work: Troubleshoot Flash Player installation | Windows
I have tried to check though Adobe's bug report forum, but every response is either "It works for us" or "we can't reproduce your error" ......HUH? https://bugs.adobe.com/jira/secure/IssueNavigator.jspa
Unfortunately when you use the link you will have to re-set the parameters for Flash again.
Some responses from Tech net: Unable to install Adobe Flash Player: Error message "Unable to authenticate install"
This one looks promising from Kashile: Unable to install Adobe Flash Player: Error message "Unable to authenticate install"
I am planning on running the debugger, and the SubInACL tool: Canā€™t install Flash Player | Windows registry permissions
There are steps in this link that may work: Adobe Flash Player trouble - Internet EXP 8 [Solved]
This all boils down IMHO that adobe is using outdated certificates for their flash installations. But, why does it work for some IE8's, and not for others?
But I sure when someone would ask them, their response would be either "It works for us" or "we can't reproduce your error" ......HUH?
Well, it is getting late for me here on the right coast, (12:34am est) its snowin' agin' with freezing rain later on, so I'm going to cruse the forum for awhile then get to bed.
I'll try those last couple of fixes later today, and report back.....