Oh, that's not good.

As a quick test to see whether one of your extensions might be causing this, could you test the page in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using

Help > Restart with Add-ons Disabled (Flash and other plugins still run)

In the dialog, click "Start in Safe Mode" (not Reset)

Any difference?

Seems to have solved the problem - I guess I now need to add in each add on - one at a time - to isolate the critter ?

Looks like it is RSS Icon 1.0.6

I will learn to live without it :)

You can try this extension instead:

• https://addons.mozilla.org/firefox/addon/rss-icon-in-url-bar/

• https://addons.mozilla.org/firefox/search/?q=RSS