When logging in using Chrome, this error shows up using trunk:
Warning: session_regenerate_id() [<a href='function.session-regenerate-id'>function.session-regenerate-id</a>]: Session object destruction failed in D:\piwik\svn\trunk\libs\Zend\Session.php on line 313
Backtrace -->
<a href='/0'>#0</a> Piwik_ErrorHandler(2, session_regenerate_id() [<a href='function.session-regenerate-id'>function.session-regenerate-id</a>]: Session object destruction failed, D:\piwik\svn\trunk\libs\Zend\Session.php, 313, Array ([filename] => ,[linenum] => 0))<a href='/1'>#1</a> session_regenerate_id(1) called at [D:\piwik\svn\trunk\libs\Zend\Session.php:313]<a href='/2'>#2</a> Zend_Session::regenerateId() called at [D:\piwik\svn\trunk\plugins\Login\Login.php:139]<a href='/3'>#3</a> Piwik_Login->initSession(Piwik_Event_Notification Object ([_notificationName] => Login.initSession,[_notificationObject] => Array ([login] => root,[md5Password] => 098f6bcd4621d373cade4e832627b4f6,[rememberMe] => ),[_notificationInfo] => Array (),[_notificationState] => 0,[_notificationCount] => 0))<a href='/4'>#4</a> call_user_func_array(Array ([0] => Piwik_Login Object (),[1] => initSession), Array ([0] => Piwik_Event_Notification Object ([_notificationName] => Login.initSession,[_notificationObject] => Array ([login] => root,[md5Password] => 098f6bcd4621d373cade4e832627b4f6,[rememberMe] => ),[_notificationInfo] => Array (),[_notificationState] => 0,[_notificationCount] => 0))) called at [D:\piwik\svn\trunk\libs\Event\Dispatcher.php:284]<a href='/5'>#5</a> Event_Dispatcher->postNotification(Piwik_Event_Notification Object ([_notificationName] => Login.initSession,[_notificationObject] => Array ([login] => root,[md5Password] => 098f6bcd4621d373cade4e832627b4f6,[rememberMe] => ),[_notificationInfo] => Array (),[_notificationState] => 0,[_notificationCount] => 0), , ) called at [D:\piwik\svn\trunk\core\PluginsManager.php:608]<a href='/6'>#6</a> Piwik_PostEvent(Login.initSession, Array ([login] => root,[md5Password] => 098f6bcd4621d373cade4e832627b4f6,[rememberMe] => )) called at [D:\piwik\svn\trunk\plugins\Login\Controller.php:142]<a href='/7'>#7</a> Piwik_Login_Controller->authenticateAndRedirect(root, 098f6bcd4621d373cade4e832627b4f6, ) called at [D:\piwik\svn\trunk\plugins\Login\Controller.php:53]<a href='/8'>#8</a> Piwik_Login_Controller->login() called at [D:\piwik\svn\trunk\plugins\Login\Controller.php:28]<a href='/9'>#9</a> Piwik_Login_Controller->index()<a href='/10'>#10</a> call_user_func_array(Array ([0] => Piwik_Login_Controller Object ([] => Login,[] => ,[] => ,[] => 0,[] => Piwik_Site Object ([] => 0)),[1] => index), Array ()) called at [D:\piwik\svn\trunk\core\FrontController.php:127]<a href='/11'>#11</a> Piwik_FrontController->dispatch() called at [D:\piwik\svn\trunk\index.php:57]
Maybe it showed up because Live! was running at the same time? Some kind of concurrent session conflict?
That's the most likely cause. Php implements its own session file locking.
We can handle this when we implement #1279.