Davinci Crashed when trying to save project (Windows)

I've been using the beta 6 version in Windows 10 with few problems until recently when I've had two bad crashes. The 2nd (and prob 1st also) was while saving a project with 2160p foortage in a 2160 timeline. The save started ok but hung at 21%. I then waited 15mins or so but the project wouldn't respond - two greyed out windows - the project and a note about Davinci not responding. Eventually tried to shut it down using Task manager but the grey windows remained and I couldn't close down my computer properly. After waiting a while again I switched the power off. On restarting, the SSD i use for "active" media and the cache wasn't recognised and in Disk manager I was asked to intialize the Disk. On the first occasion, after a few restarts Windows 'rediscovered' the SSD, this time though no such luck so far. If DaVinci hangs is there any point in waiting say several hours before giving up and turning the power off? Thanks in advance to anyone who responds.