silverlight

Try a different browser.

I have the same issue, I just upgraded Lion to Mountain Lion and Silverlight does not work any more on either Safari, Firefox or Chrome. Apperently the latest version of Silverlight is out of date, according to the message I get. But it keeps telling me to download the same "old" version.

And no, starting Firefox in 32 bit mode is not a solution either.

This has to be a known problem?

Safari, Silverlight, Fidelity Investments, ActiveTraderPro.com . Silverlight is problematic. It does not play well with Safari and other browsers. With that said, I am no expert. I have a MacBook Air Fall 2010 with OS X 10.10.3 and the latest Silverlight. For sometime (most of 2015), Fidelity Investment's ActiveTraderPro.com site which unfortunately uses Silverlight has not been operational on my Mac. No real help available from anyone and hard to find an answer. I used CleanMyMac (a disk Utility) to remove Silverlight and all of its components (not just the app). I rebooted the Mac. Downloaded Silverlight from Fidelity "1 more time" and it did not work. I changed the Safari Security Preferences to always allow Silverlight to run in Unsafe Mode when using Fidelity's web site. It now works. I have done the delete / reinstall / set Security Preferences to Unsafe Mode for Silverlight many times, but this was the first time I used CleanMyMac to delete all of Silverlight's files (visible and non-Visible). This time it worked.

By the way, I was able to run ActiveTraderPro using Firefox, but that was not what I wanted to do. I wanted Safari. Good Luck.