[Andreas]

Regarding the cpnav problems in conjunction with my Enhanced ACP Navigation Hack:

By setting mater="true", your XML effectively becomes the parent of navgroup users, if it is loaded before cpnav_vbulletin.xml - which is the case on UN*X-systems, but not on Windows:

[110] => Array
        (
            [Users] => Array
                (
                    [options] => Array
                        (
                            [10] => Array
                                (
                                    [Add New User] => Array
                                        (
                                            [displayorder] => 10
                                            [phrase] => add_new_user
                                            [link] => user.php?do=add
                                            [text] => Add New User
                                        )

                                )

                            [...]

                            [900] => Array
                                (
                                    [mh_unm_username_history_search] => Array
                                        (
                                            [displayorder] => 900
                                            [phrase] => mh_unm_username_history_search
                                            [link] => mh_unm_history.php
                                            [text] => Username History Search
                                        )

                                )

                        )

                    [group] => Array
                        (
                            [phrase] => users
                            [permissions] => canadminusers
                            [displayorder] => 110
                            [nav_file] => mh_unm
                            [text] => Users
                        )

                )

My code expects, that if a group is created by a cpnav XML other than vbulletin, that it is a custom group - hence Users disappears from the main page in this case.
You should not set master, if you are adding to existing groups.
Though I will modify my code to add an additional check for known vBulletin groups.