I tend to get the same, first lock up after around 5-15 mins and the next one after a reboot around 9 hrs later.
Im just gonna deal with it for now until CGMiner fully supports these. I really cant be bothered formatting the SD card, following the adafruit tutorial and getting CGMiner working again.
Just ran PS -ef on mine and also see high CPU useage
root 2108 2106 28 04:50 ? 01:06:53 python PiMiner.py
root 2109 2106 70 04:50 ? 02:44:05 ./fractalbc/cgminer/cgminer --co
Perhaps its due to how I run cgminer. (nohup) is there a better way to spawn a process that keeps running all the time?