Recently I experienced strange behaviour from my ZX Evo. Games didn't load, flashing a new ERS or Custom ROM went bad if done from ERS instead of Test&Service FW, etc.
It turned out to be a faulty old SD card. IF you want to laugh, here's the thread at the TSLabs forum where I reported it: http://forum.tslabs.info/viewtopic.php?f=31&t=416