WiFi icon keeps blinking, can't turn it on or off
I solved it by deleting /data/misc/wifi/wpa_supplicant.conf.
It will reset all your saved networks.
I have it rooted and deleted the file through a root explorer or you can remove it via ADB (adb shell rm -r /data/misc/wifi/wpa_supplicant.conf. I'm not sure).

You may backup it before, then open with a text reader to see your saved passwords.