3 days ago I've updated Ubuntu 12.04 LTE on our server (mainly to get new OpenSSL libs), rebooted, everything was fine. Then after 6 hours server stopped to respond. I rebooted again and it was works for 12 hours. Then it halted.
This morning after another reboot I've found "bad_area_nosemaphore" and "do_page_fault" messages on the screen.
Again the server stopped to respond, but after reboot it started without errors.
What can cause such a problems and how to fix them?