Posts page gives 404

Without warning, my posts page has started giving a 404, and I am at a loss to know why or what to do about it. Yes, I have posts – these are all visible, but not the posts page.

Reading settings are such that my front page is a static page (‘welcome’) and my posts are on a posts page (‘news’). Both /welcome and /news are actual WordPress pages. Changing the overall permalink structure has had no effect, whatever settings I’ve used (it has an effect on the individual posts, but doesn’t make the 404 go away), and changing the individual permalink of the news page has also had no effect (changing it to /latest, for example).

If I change the reading settings to use a different page as the posts page, then the /news page suddenly shows up, proving that it is there. However, the new posts page (/about, for instance) now gives the 404.

All the other posts I’ve seen about this issue have either gone unanswered and unresolved, or the issue has been solved by changing the permalink structure to default and back again, but that doesn’t help. So I’m now really frustrated. Any ideas, anyone?

Thanks.