New Post permalinks giving 404 error

I’m maintaining a site and all was going smoothly till today. The front page is static, and posts go to ‘News’.

When I post all seems to be well, and the post appears at the top of the ‘News’ page. But when I click the title to go to the individual page I get a 404 – not found.

This happens for any new post I make as of this morning. Permalinks to older posts work fine. I have done a lot of work on the site today – but only adding new pages etc. The only config change I’ve made is to change the default category from ‘uncategorized’ to ‘news’.

My permalink structure is /%category%/%postname%/

I’ve tried the following :
– changed theme (error was the same)
– deleting and recreating the posts
– changing the post name to update the slug
– manually changing the slug
– editing the posts
– the problem is still there.

Any suggestions as to where I go next?

I don’t want to restore to backup – too much done since the last one. I’m OK to check mySQL databases if absolutely necessary, but would rather resolve through the front end…