When checking for admin rights most places of the code compare the users rights
for the "sysop" flag. But several other places check for a flag called
"siteadmin" instead. With current HEAD code this leads to the situation that the
installer gives "sysop" to the first admin, but that admin can't do anything on
the special pages cause special pages check for "siteadmin" (via
$wgAvailableRights in Define.php).
Also bureaucrats can't access their special pages as the "bureaucrat" flag is
missing in $wgAvailableRights too.
Maybe "hashar" can bring some light into that problem as he changed the user
rights implementation at 2004-10-24 in User.php and Defines.php.