I've recently had the problem, that the phone, booted up with WiFi on, stuck at 1GHz with full load by the system_server process. After examining logcat, I've discovered an message regarding keystore & bad file number. Also, I couldn't get into settings->security anymore, process FC. After some research, I've flashed the system ROM again (e.g. CM10.1) and since that, the error was gone. No more stuck at full speed & full load when booted up with WiFi on.