3) If it seems to have rebooted and is still locked, I found it often had not rebooted yet and I had not waited long enough. Also, try "coldreboot" from the command line.
Next time, try "shutdown -rn now"
This skips the whole init process and shuts all services immediately, even hung ones.
There have been a few times that I have had it lockup so bad I had to physically reboot it... And all but one of those has been because of a failed USB stick I was using as a drive (But at $5 a crack, and BAMT so easy to configure, I will likely keep using the cheap ones...)
And that is the mistake. Cheap ones you'll buy more often makes them being expensive ones. plus, a cheap stick has cheap flash cells without any wear leveling and maybe built-in errors that occur when the stick is only written often enough. The cow debian live system and noatime mounting of file systems doesn't help on that much.
Better stick (pun intended) to brands like Kingston, SanDisk or the like. They are way faster than the cheap ones, anyway....
A more general thought on this one:
Successful mining is about stability. You can't afford your miners being down all the time because of outages due to overclocking, cheap disks/sticks, exploding PSU's, overheating cases, overheating houses
or anything else that stops your cards from doing billions of hashes per second. Think about it.