things done:
1. put site in maintenance mode
2. copied all drupal files thru ftp (except the sites folder)
3. run update.php
after I went to front page, these error showed up
Notice: Undefined variable: tab_root_map in _menu_translate() (line 749 of .../includes/menu.inc).
Warning: implode(): Invalid arguments passed in _menu_translate() (line 749 of .../includes/menu.inc).
Notice: Undefined variable: tab_parent_map in _menu_translate() (line 750 of .../includes/menu.inc).
Warning: implode(): Invalid arguments passed in _menu_translate() (line 750 of .../includes/menu.inc).
did I do something wrong?