Edit your question if its similar. If you've encountered a new problem, ask a new question.
The answers can be edited, too. It wouldn't hurt to leave a comment on questions that have the potential to become non sequiturs after your edit, just so the authors of those answers can go back and revise them. If all of the answers will become blatant non sequiturs, then that is probably a good sign that you need to ask a new quesiton.
An example of one I had today was a guy was trying to store a value from a SQL query in a portion of SSIS. I had answered that literal question, and then John Saunders comes through and goes, "Oh, you need this," which was the correct way to do what the OP actually wanted to get to. I was too busy just answering the bloody question to notice. The question got edited and John's post prevailed, while I deleted mine.