The most common cause of difficulties in downloading YouTube videos comes from accessing the secure https version of YouTube as opposed to the regular http version of the site. RMC5 will not download secure streams. Try visiting http://www.youtube.com. If the http switches back to https, please use the troubleshooter linked-to below.
A secondary cause of trouble comes with newer high speed internet connections and Internet Protocol Version 6 being used. Internet Protocol Version 6 (TCP/IPv6) needs to be turned off - it will not affect your connection speed.
Here is our online troubleshooter for identifying and addressing these problems:
http://applian.com/replay-media-catcher/troubleshooter/replaymediacatcher-downloading-version