My lumia 520 had huge trouble with this latest preview version. The cogs kept spinning with no sign of the worm even emerging. I got up the next morning to see my phone switched off. I Connected the charger and just the battery icon kept flashing. Hitting the soft reset brought back the spinning cogs. Hoping that it was bricked, I started downloading the recovery tool, when all of a sudden the worm at the spinning cog emerged and met the end in about 5 minutes. Tada...my phone was back. Any way why did this **** happen?