Working on a Drupal site that's already half-way started, I noticed that after installing the admin_menu module many links I expected were missing, such as the refresh cache links and several content types under the Content Types menu.

First, I tried clearing out all caches manually via the Performance page.

Next, I tried truncating all cache tables in case cache_menu or another table was corrupted.

Still no go, so I tried disabling, uninstalling, and reinstalling the admin_menu module which should rebuild the admin_menu links in the menu router.

In the end it turned out to be a Wampserver problem as it (as well as Xampp) use PHP 5.3, which Drupal has a lot of problems with. PHP 5.3 has a change from earlier versions in that function declarations like:

function admin_menu_admin_menu(&$deleted)

no longer work. Normally, you'd see that in your error messages.

The solution is to remove the & before $deleted on line 107 in admin_menu.inc in the admin_menu module. This will also make the related PHP warnings go away.

Running 5.2 and 5.3 on one computer using XAMPP (on OSX) is easy by following these instructions: https://gist.github.com/1012774