This is a great script, but it needs two fixes.

Most recently, it needed the line

mediaSource = "http://dl.redtube.com/_videos_t4vn23s9jc5498tgj49icfj4678/" + v_fileFloat + "/" + mapping + ".flv";

changed to

mediaSource = "http://dlembed.redtube.com/_videos_t4vn23s9jc5498tgj49icfj4678/" + v_fileFloat + "/" + mapping + ".flv";

A few months ago, it needed another change.

if(hrefNodes[a].getAttribute('href').substr(0,28) == "http://www.redtube.com/share")

changed to

if(hrefNodes[a].getAttribute('href').substr(0,7) == "/share/")

I recently found that this script had stopped working. Instead of downloading the actual flv file it would just download a file with the same name that is just 162 Byte html code segment containing the "404 Not Found" error. I had previously applied the older fix, I have now applied the most recent update and it isn't fixing the new issue.

Redtube now have an onClick element to the link, require an extra hash at the end of the URL, and have once again changed the first part of the link.

In addition to the above change to using "/share/" not "http://www.redtube.com/share" you will need to do the following.

Under
hrefNodes[a].setAttribute('href', mediaSource);
add
hrefNodes[a].setAttribute('onClick', '');

Replace the
mediaSource = "http://...
line with

      mediaSource = "http://dl.redtube.com/467f9bca32b1989277b48582944f325afa3374/" + v_fileFloat + "/" + mapping + ".flv";
      var element = document.getElementById('redtube_flv_player');
      if (element != null) {
        dim_re = /.*&hash_flv=(.*?)&.*/g;
        m = dim_re.exec(element.innerHTML);
        mediaSource = mediaSource + m[1] + "?start=0";
      }

This works with FIrefox 3.5 not sure about other browsers.