It could be EMF interference. Build a tinfoil cage or metal mesh like screening, ( see faraday cage) around the cube(s) leaving plenty of space for airflow and wrap a couple turns of your lan cable around ferrite core.
Also, its been reported that android phones using your local WiFi network can cause cubes to lock. A couple of of my Cubes had the same problem. Sometime they would run for days, or a few hours when they would just stop and the red status light would stop blinking. Found out that a local Amatur radio operator transmissions would cause these two to lock up when he was transmitting.
My take on the "tinfoil cage" is that is is rather far-fetched. The only instance where I have seen this used is in scientific research with extremely sensitive probes (Squid ion channel investigation) and inside the antenna field of a 43,000 watt AM transmitter. There are just to many other failure modes that are well established. While the procedure will not hurt insure the airflow is not reduced thus increasing the chip temperatures.
It seems that there is an Android on WiFi router problem, It has to do with it ignoring the DHCP lease times.
Full information can be found on theAndroid Open Source Project Issue Tracker: DHCP client ignores lease time:
https://code.google.com/p/android/issues/detail?id=11236One thing that may help is to make sure the Cube(s) and any proxy are on addresses outside the DHCP pool so there will not be any collisions.
With or without Android insure the proxy address is either statically assigned outside the DHCP pool or set to always get the same address from DHCP, this will prevent a new proxy address stopping mining.