Check for 'access arguments' => user_access(...)

If you do a search for site:drupal.org menu.inc line 258 you'll see a whole bunch of people with this issue. It stems from an incorrect port of Drupal 5 to Drupal 6 code.

In the old Drupal 5 code you'd do:

'access' => user_access('banana');

In the new Drupal 6 code that would be:

'access arguments' => array('banana');

but apparently lots of people are missing this and instead doing:

'access arguments' => user_access('banana');

This is passing a boolean where menu.inc expects an array, and hilarity ensues!