I use lastest FW, and just 1hour ago, one of them stopped working.
Cgminer is running ,but hash is 0 Mhz. I try all firmware, and restart ,it doesnt work.
Old Fw say it is sick.
what's wrong? Asic chips are broken??

I understand your frustration, as I have the same issue.
Didn't find a way around it yet.
I did install last Saturday a testing version of the firmware, since then no lockups anymore...
http://downloads.qi-hardware.com/people/xiangfu/avalon/next-testing/Edit: when my Avalon showed sick, I've opened the unit and reattached all cables and power cycle the machine. Since then I didn't see the sick status anymore
thanks,mu FW is 0410,and I will reconect cable today.
but find , I sleep like a pig this night :-)