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.
Also refer to the following threads for the discussion on the same :
What is your operating system & version?
What is your web browser?
[topic moved to Flash Player forum]
My OS is Mozilla Firefox