I've had Windows 8.1 installed for about a month and it's been working fine. Ever since a day or two ago though, it's been freezing when left idle for a while. The mouse can move but nothing responds to anything. This problem seems to me to have started after installing updates KB2884848, KB2883200, and KB2895219, although I can't be sure of this
If you Google KB2884848 you will find a lot of complaints regarding this bug,
Could this be due to the hardware restricting UEFI-secure boot?