User Avatar plugin not working since upgrading to 3.0

Clicking on the Edit link in the Avatar column on the Super Admin/Users page returns “Apologies, but the page you requested could not be found. Perhaps searching will help.”

The page it’s trying to access is

I had a similar problem with the Messaging plugin. The issue was resolved by replacing inbox.php, which was deleted when wp-admin was deleted as per the instructions at

I have checked and options-discussion.php is in the wp-admin folder as per the plugin installation instructions.

Any help would be greatly appreciated.