As reported in my previous post, WordPress MU has a bug where if you enable the Plugin menu, then disable it, you will not be able to re-enable it. To re-enable the Plugin menu, go into your PHPMyAdmin interface, open the database for your WordPress MU site, open the wp_sitemeta table. Switch to the browser tab, rather than the structure tab. Locate the menu_items meta key. It should have an empty meta value, based on what I have observed, and what others are saying. Delete this meta key by hitting the red x. Now you will be able to re-enable your Plugins menu. Note that if you re-disable the Plugin menu option, you will have to re-delete the menu_items meta key in order to re-enable it :) A quick and dirty solution to one headache of a simple problem. I expect this bug to be resolved in the next version of WordPress MU.