Hi, try another browser. If that's OK, restart Firefox. If the problem persists, try a Clean Reinstall; this means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location. With Firefox closed, use another browser to download Firefox from https://www.mozilla.org/en-US/firefox/all/ and save the file to somewhere convenient on your computer.

Now delete the Firefox installation folder which should be in one of the following locations -

C:\Program Files\Mozilla Firefox C:\Program Files (x86)\Mozilla Firefox

You can now double click the file you previously downloaded to install Firefox.

If you see it in another browser, try updating your PC's graphics driver Upgrade your graphics drivers to use hardware acceleration and WebGL

If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!

Hi Scribe & thanks for your post. I did as you suggested and tried Windows explorer and everything works fine, then tried a Firefox re-install 3 times but I still have the same problem.

Hi all, Just to let anyone who might have seen my original post that I have now solved it. After days of seeking an answer and of the problem going worse, I spotted a reply to someone else who had a similar problem a few years ago. "try a mouse replacement". So I did, and it solved the problem!! Simple.