Mine got fixed by a Microsoft engineer. He spend about 2 hours on my machine.
In fact he pointed me to following hardware requirement for installing Windows 8.1
http://windows.microsoft.com/en-us/windows-8/system-requirements
“To install a 64-bit OS on a 64-bit PC, your processor needs to support CMPXCHG16b, PrefetchW, and LAHF/SAHF”
This would result in different drivers being supported for Windows 8 and Windows 8.1 (and even different Wifi adapters on the same machine not being supported.
f.ex. For my Acer Aspire E1-571 there are Windows 8 drivers for network adapters from Broadcom, Atheros and Intel. For Windows 8.1, only the Atheros adapter has a driver supported by Acer. (see http://us.acer.com/ac/en/US/content/drivers )
My machine has an Intel adapter. But - if I got it correctly - he had it fixed by
- Keeping the last Intel driver (15.10.5.1 31-Oct-13 , I believe the date is important here)
- Right-click ‘Command prompt’ > Run as an administrator: ‘netsh int ip reset C:\resetlog.exe’
- turn off the “Allow the computer to turn off this device to save power” in the network adapters power settings pane
Looks like a mixt of all solutions I’ve seen before. The PC is steady since 4 hours (including 3 reboots). But I’ll keep you updated if would change its mind.