Suddenly unable to access plugin-specific settings

“You do not have sufficient permissions to access this page” but only for settings pages added by plugins.

which plugin is it?
downloaded from?

Any plugin. All of them.

Verified that permissions on my wp-content/plugins is 755. So that’s not the problem.

Debugging info:

You do not have sufficient permissions to access this page. 

Array
(
    [Pages No Access] => Array
        (
            [edit-tags.php?taxonomy=link_category] => 1
        )

    [User Info] => WP_User Object
        (
            [data] => stdClass Object
                (
                    [ID] => 1
                    [user_login] => xxx
                    [user_pass] => ZZZZZZ
                    [user_nicename] => xxx
                    [user_email] => EMAIL
                    [user_url] =>
                    [user_registered] => 2011-12-28 22:36:10
                    [user_activation_key] =>
                    [user_status] => 0
                    [display_name] => xxx
                )

            [ID] => 1
            [caps] => Array
                (
                    [administrator] => 1
                )

            [cap_key] => myprefix_capabilities
            [roles] => Array
                (
                    [0] => administrator
                )

            [allcaps] => Array
                (
                    [switch_themes] => 1
                    [edit_themes] => 1
                    [activate_plugins] => 1
                    [edit_plugins] => 1
                    [edit_users] => 1
                    [edit_files] => 1
                    [manage_options] => 1
                    [moderate_comments] => 1
                    [manage_categories] => 1
                    [manage_links] => 1
                    [upload_files] => 1
                    [import] => 1
                    [unfiltered_html] => 1
                    [edit_posts] => 1
                    [edit_others_posts] => 1
                    [edit_published_posts] => 1
                    [publish_posts] => 1
                    [edit_pages] => 1
                    [read] => 1
                    [level_10] => 1
                    [level_9] => 1
                    [level_8] => 1
                    [level_7] => 1
                    [level_6] => 1
                    [level_5] => 1
                    [level_4] => 1
                    [level_3] => 1
                    [level_2] => 1
                    [level_1] => 1
                    [level_0] => 1
                    [edit_others_pages] => 1
                    [edit_published_pages] => 1
                    [publish_pages] => 1
                    [delete_pages] => 1
                    [delete_others_pages] => 1
                    [delete_published_pages] => 1
                    [delete_posts] => 1
                    [delete_others_posts] => 1
                    [delete_published_posts] => 1
                    [delete_private_posts] => 1
                    [edit_private_posts] => 1
                    [read_private_posts] => 1
                    [delete_private_pages] => 1
                    [edit_private_pages] => 1
                    [read_private_pages] => 1
                    [delete_users] => 1
                    [create_users] => 1
                    [unfiltered_upload] => 1
                    [edit_dashboard] => 1
                    [update_plugins] => 1
                    [delete_plugins] => 1
                    [install_plugins] => 1
                    [update_themes] => 1
                    [install_themes] => 1
                    [update_core] => 1
                    [list_users] => 1
                    [remove_users] => 1
                    [promote_users] => 1
                    [edit_theme_options] => 1
                    [delete_themes] => 1
                    [export] => 1
                    [NextGEN Manage tags] => 1
                    [NextGEN Manage others gallery] => 1
                    [access_gtmetrix] => 1
                    [wpseo_bulk_edit] => 1
                    [administrator] => 1
                )

            [filter] =>
        )

    [Roles] => Array
        (
            [administrator] => Administrator
            [editor] => Editor
            [author] => Author
            [contributor] => Contributor
            [subscriber] => Subscriber
        )

)

Decided to sleep on it. This morning, I find the problem isn’t there anymore. NO IDEA

Glad to know it ??