Persistent Blocked Plug-In Dialog on MacOS 10.6.8 and Safari 5.1

Your post seemed unique from the other thread, so I branched this out to a new discussion.

You mentioned that you download the installer repeatedly and that Flash Player is registered.  I just wanted to confirm that you went to your Downloads folder and executed the installer once it was downloaded.  As you ran the uninstaller and rebooted, I'm guessing that you did, but I don't want to assume and send you in circles.

I don't have a great suggestion.  It's Safari doing the blocking.  Typically doing a clean uninstall and reinstall will resolve this in the event that Safari gets "stuck" and doesn't see the updated version, but it sounds like you've tried that.

You can try enabling Flash Player manually, which may get you around the problem (at least temporarily):

How to re-enable older Flash in Safari 5.1.7 - CNET

Therefore, if you need to revert back to a prior version of Flash when using Safari 5.1.7 or higher, you can re-enable the plug-in by going to the Macintosh HD/Library/Internet Plug-Ins (Disabled)/ folder and moving the "Flash Player.plugin" file from this folder into the Macintosh HD/Library/Internet Plug-Ins/ folder (the one that does not have "Disabled" in its name).

I'm wondering if this is a filesystem permission problem, and we're just not able to successfully write to the directory where the enabled plug-ins live.  (You may run into this when attempting the above instructions)

If that's the case, repairing the filesystem and filesystem permissions might resolve this - see the section on First Aid here -- run both Verify and Repair Filesystem and Verify and Repair Disk Permissions (sometimes the verify permissions step will return clean, then repair will fix a bunch of stuff):

Resolve startup issues and perform disk maintenance with Disk Utility and fsck - Apple Support