Avast reported that i had malware on my nexus 7 and then the malware reporting window started to flash quickly. After a struggle I managed to turn the tablet off and on and and succeeded to do a factory reset. Went to charge the nexus but it would not charge. I am using the correct charger and lead (checked these were working by charging my phone ok). then got a no command error so got it into safe mode but it still did not charge. Did another factory reset but same problem. Solved: I had an intermittent break in my charging cable.