Does the “Whoa there!” page have a URL like:
https://api.twitter.com/oauth/authorize?oauth_token=h1T93AAAAAAAAAAbAAABUwBXxto
or
https://api.twitter.com/oauth/authorize?oauth_token=
If it’s the second one the server is having issues getting a request token and you probably don’t have there right consumer key/secret or the clock on server is not accurate.