Finally, Sony made a phone that is exactly what I always wanted. 720p HD resolution on 4.5" screen, enough memory, big battery, good camera and dust and water proof. You can read positive reviews all over the web, so I won't bother adding another one.

After a week of being a happy Sony Xperia ZR owner, my wifi stopped connecting to networks. I can't connect to any network I have tried, but the list of networks is ok. It stopped working suddenly. My previously used networks are all marked as "Saved", but when I try to connect the following happens:

1. Saved (doesn't even change when tapped)
2. Connecting -> Saved
3. Connecting -> Authentication problem -> Saved

This is what I have tried to fix it:

1. Restart phone
2. Restart phone, take out battery, SD card and SIM card
3. Restart wi-fi router
4. Connect to another network (sometimes works with some networks)
5. Forget network -> Type password again
6. Connect another Android device to the same network
7. Connect another non-android device to the same network
8. Change the router wireless settings to WEP, WPA and unsecured
9. Factory reset of the router
10. Sony Companion -> Repair
11. Factory reset of the phone

And nothing worked. I packed the phone into the box ready to go to service centre and went to cook a delicious stew which took about 3 hours and filled my apartment with heavenly smelling goodness. I came back to check whether there are any data in the phone and it started to work again. Just like that. I did not do anything.

But my joy lasted only for a while, because after the phone lost the wifi connection, it didn't connect again. I took the phone to work to try more wifi access points. I have tried about 10 of them on the way there and three more in the office. Same result. I tried to dig deeper and this is what I found in LogCat:

09-18 09:10:12.130: W/wpa_supplicant(3838): wlan0: Failed to initiate AP scan
09-18 09:10:12.811: I/wpa_supplicant(3838): wlan0: Trying to associate with (here is the router MAC) (SSID='smartus@unifi' freq=2427 MHz)
09-18 09:10:14.023: I/wpa_supplicant(3838): wlan0: CTRL-EVENT-ASSOC-REJECT bssid=(here is my router MAC) status_code=1
09-18 09:10:19.088: I/WifiManager(2391): Process ndroid.settings requested an active scan
09-18 09:10:22.812: I/wpa_supplicant(3838): wlan0: Authentication with (here is the router MAC)

Same thing for every router. Sometimes the connection went through and then I would connect for a while. CTRL-EVENT-ASSOC-REJECT should only happen when the network is too busy and the AP rejects your connection attempt. I think the phone simply started to misinterpret signals from the router.

I took the phone the service centre, where they tried to flash upgraded ROM, but it did not help and the case was closed with the conclusion "faulty hardware".

I hope nobody will ever need to read this article. But if you are reading it, because you have the same problem, it might be hardware issue.

Update

The phone body was replaced. Wi-fi works very well now, but will wait for two weeks to make the final conclusion!

Update 2

The phone seems to work after another two weeks. No issues with wi-fi. Hopefully it's gonna stay this way. Also this article made it to TOP 5 articles this month. Looks like this is pretty common issue.

Update 3

Xperia user Emmanuel suggested that it might be a software issue caused maybe by a faulty hardware. The wi-fi region code gets set to wrong value or unset. If you have a rooted phone, you can try fixing it by this software: http://forum.xda-developers.com/showthread.php?t=1982149

My phone however didn't have a problem with wi-fi since they replaced the body.

Update 4

Update to Android 4.3 Jelly Bean has been released recently. Try it as an option too.

Funny note

Anybody noticed that all new Sony Xperia phones pictures have the same screen? It always says Thursday January 3, 10:35. Somebody was very lazy... Just for comparison, Xperia Z and Xperia ZR. But you will see it on pictures of all Xperias from this year.