Came here because my local piwik told me to post this. It happened on the login screen, and then I had to refresh a few times before I could actually log in. After that everything seems to be working fine again.
There is an error. Please report the message (Piwik 1.12) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).
Warning: file_get_contents(http://api.piwik.org/1.0/getLatestVersion/?piwik_version=1.12&php_version=5.2.6&url=http%3A%2F%2Fstartester%2Fpiwik%2Findex.php&trigger=&timezone=America%2FLos_Angeles) [function.file-get-contents]: failed to open stream: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. in D:\Data\htdocs\piwik\core\Http.php on line 395
#0 Piwik_ErrorHandler(…) called at [:]
#1 file_get_contents(…) called at [D:\Data\htdocs\piwik\core\Http.php:395]
#2 Piwik_Http::sendHttpRequestBy(…) called at [D:\Data\htdocs\piwik\core\Http.php:82]
#3 Piwik_Http::sendHttpRequest(…) called at [D:\Data\htdocs\piwik\core\UpdateCheck.php:62]
#4 Piwik_UpdateCheck::check(…) called at [D:\Data\htdocs\piwik\plugins\CoreUpdater\CoreUpdater.php:82]
#5 Piwik_CoreUpdater->updateCheck(…) called at [:]
#6 call_user_func_array(…) called at [D:\Data\htdocs\piwik\libs\Event\Dispatcher.php:284]
#7 Event_Dispatcher->postNotification(…) called at [D:\Data\htdocs\piwik\core\PluginsManager.php:674]
#8 Piwik_PostEvent(…) called at [D:\Data\htdocs\piwik\core\FrontController.php:303]
#9 Piwik_FrontController->init(…) called at [D:\Data\htdocs\piwik\index.php:46]
You are currently using PHP 5.2.6.