janlyons said

firefox icon suddenly has red circle and line through it - like a no smoking signal

Where do you see this  ?

Could you provide a screenshot  ?

If you need help to create a screenshot, please see : How do I create a screenshot of my problem?

Once you've done this, attach the saved screenshot file to your forum post by clicking the Browse... button below the Post your reply box.

However, if this is in Thunderbird, you can post this question on their support forum :

https://support.mozilla.org/en-US/questions/thunderbird

(just click on 'Ask a Question' at the top of the page)

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

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

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

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

thanks - a computer guy stopped by my neighbors so asked him to fix it and he did -not sure how but working fine again. Thank you