I've got a Sony Via Pro 13.3 (4th generation i7 cpu) and have installed the RTM version of windows 8.1. I'm getting the same results: flickering started once I enter the Windows 8.1 start screen for the first time. I am able to boot into safe mode with networking. The display driver was 9.18.10.3200 (comes with 8.1 RTM?). I down-graded to the 9.18.10.3165 version off the Sony website for windows 8.0, but still have the flickering.
I'm trying 15.33.64.3214 (e.g. 9.19.10.3214) to see if that works.