Last night I got the 3.12.0hf3 update and since then the miner mines for about an hour and then restarts. It's not a full RPI reboot, but cgminer crashes/quits then restarts. The cgminer restarts seem to be about every 75 minutes or so. I'm running stock clocks.
Since the automatic update I'm only getting about 350-370GH/s.
Same here. You can see how the hash rate graph changes after loading 3.12.0hf3. It becomes more erratic and the little dips appear to be miner restarts.

On the pool side the hashrate has remained roughly the same (slight dip) but my stale rate appears to have gone up significantly (more than doubled).
MinePeon Version: 0.2.4.3hf7
Miner Version: cgminer3.12.0hf3