I run 10.8.2 and this problem has annoyed me for a long time. Once in a while (sometimes after one day, sometimes after several day), my browser cannot access any website, or becomes unresponsive, then I cannot quite the browser, mail or any other application. And I cannot start console. Sometimes I can reach the reboot menu, sometimes not, but the menu does not work. So I have to hold the power button to shutdown the computer. It has happened when I used Chrome, Safari and Firefox. Has anyone seen the same problem?