We've received reports from users that after upgrading the TED iPad app to version 1.6.1 they were unable to play downloaded talks without an internet connection. It turns out, this was the result of a bug in the download manager when we updated the TED app to version 1.6.1.
We've fixed this, and future downloads should be able to play offline with no issues. Unfortunately, this won't correct the problem for talks that were already downloaded to the iPad prior to the fix, so the must be deleted and re-downloaded to play successfully without an internet connection.
When we upgrade to 1.6.2 the TED app will 're-discover' these downloaded talks and re-downloading is unneccessary. However, we do not have a planned release date for 1.6.2 at this time and therefore recommend re-downloading.