Does the link open if you set focus to the location bar and click the Go button or press the Enter key ?

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Thanks for the reply, the problem is intermittent, right now it's working. When it was failing I did try to put the cursor in the address bar and hit Enter. No change, still a blank window. Another example, when I received the email you sent me about the problem, I clicking one on the two links in the email, again a blank window. But that too, is working now. When it fails again, I'll try what you suggested. Thanks.