Translated Page results in 404

I ran into this while testing an Event Organiser - Babble extension. Posts work fine and as expected, but pages do not. Details, and steps below.

I thought #151 might be related, but posts worked fine for me.

WordPress 3.9.1
Active plug-ins: Babble.
Theme: TwentyThirteen.

**Steps to reproduce:**
1. Setup languages (fr) in this case. Marked as active and public.
2. Add language switcher widget
3. Go to "Sample Page", mark as ready for translation and update.
4. Go to Translation jobs. Provide a translation (for title, slug and content).
5. Mark translation as completed and save.
6. View "Sample Page" (default translation, English)
7. Change language to French.
8. Page reloads, with the expected url. But the page itself says 404.

**Expected:**
The translated content and title.

Additionally the "Sample Page" menu link points to the English version. When switching back from French to English, the url does not change and the 404 persists. (I gather this second point is probably to be expected: if it doesn't know what page it's on, it's unlikely to know what the default page is).

Reproduce the failure with WordPress 3.9.1, Babble, TwentyThirteen, and a public French language using the listed translation steps. Trace how the translated page URL is resolved and verify that the French page displays its translated content and title, while switching languages updates the menu link and URL correctly.

Written by the indexing model from the issue text.