In addition to the above solution,you can try the following:
To unblock a software publisher:
1. In Internet Explorer, click the Tools button, and then click Internet Options.
2. Go to the Content tab, Look under the Certificates section.
3. Click on Publishers button.
4. Select the Untrusted Publishers tab.
5. Select the Publisher you wish to unblock and click the Remove button.
Przemek, this is the same exact post I made earlier today, but it is not listed under my profile anymore. It is like you somehow stole the post and posed it like it was your question. Did you do that to steal points??? I actually came back on the site to inform people I fixed it by manually installing the Adobe ActiveX from http://helpx.adobe.com/flash-player/kb/installation-problems-flash-player-windows.html and then changing a setting called TURN OFF AUTOMATIC ROOTS CERTIFICATE UPDATE to not configured in the Group Policy Editor. You can access the Group Policy Editor by typing Group Policy in the start menu search box of Win 7 and then click on the link for Group Policy Editor in the search results. From there, you click on ADMIN SETTINGS and then ALL SETTINGS to find the option. I hope this helps people, but I am not quite sure what your point in stealing my post was Przemek.
If you're still encountering the 'certificate authentication failed' error when downloading/installing from get.adobe.com/flashplayer, please try one of the following two options:
- Open command prompt (C:\Windows\System32\cmd.exe)
- At the prompt, type: Certutil –urlcache * delete
- Delete the contents of the “temp” directory (on Win7 - C:\Users\<YourUseID>\AppData\Local\Temp)