I have a blog that I use a custom permalink structure. I recently modified the blog to use a static front page and an empty 'blog' page for posts. The posts page and all post pages, category pages and pages other than the (static) front page give a 'Not Found' error ( I think a 'no post found' type error rather than a 404 error though).
If I change the permalink structure to the ugly default (?p=xxx), the problem is corrected. But any custom or predefined permalink structure causes the not found errors. I have tried changing the theme and removing the seo slugs plugin but neither of those things helped. I also tried removing the content from my htaccess file and updating the permalink structure to rebuild it, but that didnt work either.
Now I am stuck with ugly links and broken external links on my site, because even if I remove the static front page and go back to having the posts page as home page, all those pages still give not found unless I use the default permalink.