After upgrading from 3.3.0 to 3.3.5, several links in Network Admin broke.
Example: Plugins page
Several of the links on this page (e.g., "Add New", "View version x.x details", and "update now") have "wp-admin/" stripped out of the URL.
For example, the "Add New" button at the top of the page should point to:
But instead points to:
WordPress Multisite rewrite rules don't know what to do with the latter, so a 404 is returned.
This behavior was introduced in the latest update.