My WiFi does not work in Sony Ericsson
Alright, I have managed to solve the problem by looking at some XDA forums.

Basically summarized here: -


Go into the WiFi settings.
Long press a remembered WiFi.
Select Forget All Networks. You might need to do it a few times.
Press the leftmost button (the one with literally four squares) to bring up a bottom menu.
Touch Scan.
Voila! WiFi working again!


The only drawback is that you need to grab passwords for each one of them again. :-(