The following requirements are known for Tweetcrete. This is an abbreviated list as we assume that if you have Concrete5 running, you've already met most of the requirements.
When I click "Authorize with Twitter" I get an error stating "This page is no longer valid. It looks like someone already used the token information you provided..."
This could be due to the server you use to host Concrete5 having an incorrect system clock setting. For more information see this article.
Another cause for this issue is if your webhosting provider blocks outbound http requests on their firewall. This prevents Tweetcrete from completing the necessary API handshake to load your timelines.