I did some research and found the solution myself

I found this article
You Must Be Registered and Logged On To View "URL" BBCode Contents...


after this I realized that the problem was occurring because I had an account on youtube and youtube had stored cookies on my hard disk

After this it was a simple matter of removing the cookies and clearing the cache, like this
Attachment 142


And now the video downloads are back to normal, like this
Attachment 143

BRAVOOOOOOOOOOOOO