I've had two running on my RPi for the past two and a half hours with no issues. One thing I did notice is that ASICMiner's build of cgminer does not handle the frequency parameter well. When passing "--bet-clk 23", I received a ton of "BET0: Unexpected value 00 received" errors. Starting with no parameters fixed the issue. I will test with the official cgminer branch later.
On the official CGminer 4.7.0 on both the RPi and on CubieTruck I got those errors on both options. As I said in an earlier post, pulling the USB controller and putting it back may have cleared it up.