Win764 guest crashes repeatedly, sometimes with a can't run in unity mode message. I tried increasing video memory from 256 to 512MB, but that seemed to worsen the problem. Now I've turned off 3D graphics to see what's up.
Host: Linux Mint 17.1 kernel 3.18.6 32GB RAM, NVidia card GeForce GTX 760, driver 346.35
Guest: win764, 4864MB vRAM, 4vCPUs
Follow up. No crashes since removing 3D graphics .