Can you elaborate the issue by sending screenshots? By 'what's new', do you mean the acitivity stream where you post an update?
If that is the case, then you should make the 'activity' page of BuddyPress your homepage.
I would like it to always default to ask "What's new" when you go to the main url, just as it does in the demo.; currently the default page shows the "activity" page, but doesn't allow you to post.