In order for me to best assist you, can you clarify your question a bit? First off, Are you referring to the content type "Discussion", or another content type like Document, Blog Post, etc.? Next, which of the following behaviors are you seeing?
- Is the issue that you cannot view the content at all?
- Is the issue that users are no longer able to contribute to it by adding additional posts or comments?
- Or, is the issue that the discussion is now "flat", as opposed to being "threaded"?