Also ran into this issue today. I'm running CarbonROM. Before this issue started, my phone started to act strangely. It wouldn't wake up from sleep, and needed to be rebooted. My WiFi is currently working, but when I leave the house, it still thinks it's connected to my WiFi at home. It's strange. What seemed to work for me temporarily is to put the phone in airplane mode, reboot, then turn off airplane mode. I also booted into Safe Mode (which didn't work properly, maybe a CarbonROM issue?), then rebooted back normally, and everything seems to work now...
WiFi stopped working again. I did a factory reset, then installed CM11 M9, and WiFi works again. Strange... I hope this isn't a hardware problem. I read some other forums where the motherboard was swapped out.
WiFi stopped working in CM11 after a while. I guess I'll try to switch back to stock.
I did a full reinstall of the stock ROM, including resetting the tamper flags. Now it seems my wifi is working again...
With stock 4.4.4 my WiFi worked for a while, then stopped working. I did a factory reset, and cannot connect to WiFi anymore
I think I will have to RMA it. Currently in contact with Google support.