Ant Video Downloader has a version 2.4.7.15 that (the developer says) is compatible with Firefox 26. You can update from the Add-ons page. Either:

• Command+Shift+a
• Tools menu > Add-ons

In the left column, click Extensions. Then click the "gear" button above the list and choose Check for Updates.

Does that fix it?

This did solve my problem and I thank you for your input and advice. The odd thing is that I had the "update automatically' section selected and this extension was not updated. The other odd thing was that when I clicked on the "check for updates" box you suggested it told me there were no updates available but I did also click the restart Firefox option and LO AND BEHOLD after restarting Firefox it told me the update to Ant v. 2.4.7.15 was successfully downloaded. It works fine now but if I hadn't pushed for updates that weren't supposedly available the program would have kept telling me there are no updates available. Strange circumstances but I'm happy again.

Thank you ("jscher2000"). I'm impressed with the quick Firefox support system reply and am grateful my problem is solved.

Thank you for your feedback. It sounds as though the extension updates were silently or invisibly queued. Occasionally I've seen "Available Updates" appear at the bottom of the left column on the Add-ons page. I'll have to remember to suggest looking for that first, since that obviously is faster than checking again.