Be sure to check the config file, by default userid ! is typed into the line:
Code:
$config['SpecialUsers']['superadministrators'] = '1';
So check config.php for $config['SpecialUsers']['superadministrators'] = '1'; <-- Ensure the one (1) is actually there. If you cloned a site i.e. made a test site and did not change the cookie setting i.e. $config['Misc']['cookieprefix'] = 'bb'; to something different then when you login the test admincp while you were previously on the live admincp it will log you out.