I have a standard index page in a custom theme (format copied from twentyeleven), and previous_posts_link (and next_posts_link) isn't working:
+ Plugins are all disabled
+ Previous_post_link works as expected (link to single post)
+ There's nothing in the functions.php to affect it
+ I've tried regenerating permalinks
+ I've switched to Twenty Eleven (works) and back to my custom theme, does not work
+ I've tried wp_reset_query
This is index.php, posts displaying on home page as per the default WP install settings.
Any ideas of other things to try or ways to diagnose this?