I wrote application which uses Arduino Mega2560 (genuine) and Ethernet Shield (china). This application sends periodic data to my Nimbits server on Google Apps. Application works initially fine, but after couple of hours it hangs. Strange is that pressing the RESET button doesn´t solve the problem (network communication doesn't work). I have to unplug and then plug the power supply again to reestablish functionality.
I suppose the problem must be in hardware (bad ethernet shield?). Or do you think than software bug can cause such behavior?