Drupal 7 - all menus disappear after clearing the cache

Question

I've inherited a Drupal 7 site from someone and have come across a really irritating bug that I'm hoping someone can help with, for some reason if I empty the Drupal cache all the left hand menus on the site disappear. The menu is put together using menu blocks and all the settings for the block and the menu itself look correct i.e. the block is in the correct region, the menu block is attached to the correct menu and the menu has all the pages on the site in it.

In the backup of the database the cache_menu table has about 40,000 entries, if I clear it and click around the site it never goes above 40 so for whatever reason it's just not re-generating the menus.

Does anyone have any ideas what might be happening and how I can fix it?

Answer 1

Managed to fix this, turns out there's a bug in the menu block module (I was using 2.2) so upgrading it fixed the issue.

Answer 2

Are you clearing the cache_menu entries manually? I'd recommend using drush—

drush cc all

Or go to settings/performance and clear the cache.