Users who don't tweet often may experience this issue, even if Auto-Refresh is enabled. A fix will be addressed in a future release.
To resolve, send a New Tweet from TweetCaster (which can be deleted later, if necessary) and your timeline should download immediately after the tweet is submitted (if not, click the Load More button).
If you are still receiving the error or no new tweets are displayed, remove the device battery for 30 seconds and re-launch the application.
If none of the above remedies fix your issue, please try deleting and reinstalling TweetCaster.