Interestingly I have just restored my windows laptop to a backup image I created, dated 16 Dec 2014, and got my widi functionality back.
I remember finally having a working widi setup for about a month previous to this (after about a year of trying and not really knowing what I did to fix it) then suddenly it was not working mid December.Suddenly the TV would not prompt about the PIN I should input to the laptop when adding it as a device, and would either time out whilst connecting or inform me my laptop was an "unsupported device"
As we all know there are so many windows updates claiming fixes for security and functionality that they are hard to ignore and it would be impossible for me to pin point which one potentially did the damage to my widi.
Now I have restored, the screenshot below is from my windows update informing me of the updates I should install now but I'm really loathed to do this now my widi is working again.
The big 890.2MB KB2919255 would be a concern which is I'm assuming is a cumulative update so making it even harder to pinpoint the culprit.
Maybe someone who knows more about these updates could shed some light
Sytem:
Lenovo u430 Touch
Windows 8.1 Pro 64bit
Broadcom BCM943228 Wlan (which actually worked better for me more often than the Intel 7260BGN it replaced)
LG 42LS575T TV