I used this for some time until the last YouTube upgrade which stopped it (and, I believe all downloaders) from working. I rejoiced when a new working edition was announced since I'd suffered a bug that required me to visit the Activation site every time I restarted Youtube. Alas, the bug remained. I contacted Dishita and after several investigative emails, he suggested creating a new Firefox Profile. Yo-hoo! This worked.

Many thanks, Dishita for the best downloader available for Firefox. And thank you for prompt and efficient assistance with my problem.

Easy YouTube Downloader Express is a wonderful and user-friendly application. It downloads MP3 files (my particular requirement) in seconds with one-click. If you don't use it, get it.