Are you using Replay Media Catcher 4 in demo mode? If not, and you have purchased the program, you can convert straight to dvd-video using that program alone.
If you are using the demo mode (which allows full captures of Youtube videos), what format are the videos in once they are on your computer? What extension do they have on the video file? Is it .flv or .avi, or something else?
You can download a free program called MediaInfo, which will show all the details of the video file that you have downloaded from Youtube. I find the Tree view within MediaInfo to be one of the better ones.
If the video format is one that is widely supported in conversion programs, I can probably recommend a better tool for converting to dvd video for you. A good free one is AVStoDVD, though DVDFlick might be better if your video is an .flv file. And a good commercial program for conversion would be ConvertXtoDVD.
This thread is probably better off in the Video Editing forum, so I'll move it in there and leave a redirect.