After unstopping my bathroom sink. I tried tighting up all tubes, but water continues to run from the black tube

Black tube-HMMM. What pray tell is a "black tube"? Tailpiece? Cross threaded?

After te advertising did you dio it like this? How to Replace a Bathroom Drain and Sink Trap - YouTube (http://www.youtube.com/watch?v=WHIyHlnj9Vw)

Would that "black tube" be a ABS pipe coming out of the wall and is the leak coming from a compression nut? Back to you, Tom