My Raspberry Pi works well, but seems to go into semi-hibernation after a while. I have it plugged in to a composite TV and keyboard; but I usually access it through ssh from another machine after logging in locally. Sometimes it becomes unreachable by ssh, and I turn on the TV -- no display. Typing at the keyboard doesn't awaken it, even with known commands like 'sudo reboot'. I end up pulling the plug and restarting. There is a cron job running every minute logging temperature, so I can tell that the system had been running fine right up to the hard reset -- it had just become unreachable.
There's a wifi adapter, but it's plugged in to a powered hub. Any thoughts?