I started having this problem about 2 weeks ago. I first thought it was just a freak thing and rebooted several times. I tried re-flashing with PR1.3 from tabletdev site. Still, My WiFi will not see any WiFi networks. I used the healthcheck and noticed the wi-fi strength at 0%. If I used "wi-fi switcher" I would be able to turn it off but not turn it back on and would get an error "Cannot enable WLAN: 'IFCONFIG WLAN0 UP' FAILED".
I sent my n900 to NokiaUSA as it is still under warranty. After a week I was shipped back with a note unable to reproduce the problem. Now after calling back and expressing my frustration I was told that they are escalating this issue and someone will call within 24 hours about 72 hours ago!
I think my WiFi hardware is dead but am not sure. Should I try the cold flash? I couldn't understand how it works? Also, I didn't do an eMMC flash. Just the regular flash which I'm used to. What does eMMC do? I don't use a microSD at the moment as it is in another phone which I'm using. I would rather fix this problem than send my phone back to the stupid Nokia service center in Texas. If they can't reproduce a simple wi-fi connection issue, I shudder to think how they will fix my problem at the hardware level. Please help. I love my phone but can't deal with this wi-fi issue. Oh i Forgot. My 3G Data and Bluetooth works fine.

If my phone is frozen if I try to use Wi-Fi, I need to turn off and back on. However if I turn off, I cannot turn unless I remove the battery and put it back on. Something is not right I think.

I used to get this when using aircrack, and used to get very annoyed at my own stupidity lol. If you have any programs that enable monitor mode typing this in to xterminal may help.

root

ifconfig wlan0 down

iwconfig wlan0 mode Manager

ifconfig wlan0 up

Thanks Thargor. I installed rootsh and then ran the above commands. The first two ran fine. The third one "ifconfig wlan0 up" is hanging. It has been over 5 minutes and still no sign of the command prompt returning. I just see the cursor waiting. I will try to reboot and see if anything happens.

I re-flashed but this time removed the SIM card and did the eMMC and then the root flash. No luck. Same "No connections available" message when trying to look for a WiFi. Still waiting for the Nokia Tier2 call. I just want to get this fixed by them as I don't know is this is a software/firmware issue.

i got the exact problem...solution?i changed the motherboard..and everything is back to normal..

Thanks for the info one1002. Did you replace the MB yourself? Where did you get the MB and how much did it cost you if you don't mind sharing that information. My warranty runs out next month and hopefully I can have this fixed before then.

The goons... called Nokia..

So I sent the phone back to Nokia repair center in Texas. For the second time the phone was shipped back to me without repairing. This time they say there is water damage.. My phone was babied and was always in a protective case and never been near pool, humidifier etc.. I asked them why they didn't notice the water damage the 1st time.. They told me that the damage must have happened after I got the phone back the first time.. Huh? And I shipped the phone back in a few days after talking with Tier2 support and they sent me a shipping label. Wtf Nokia? You like to find excuses so that you don't have to honor your warranty? No wonder your sales suck. A very disappointed Nokia customer.

I would try calling back; don't talk to the same people. Be nice. Ask for a supervisor. Every company has subversive employees who will try to help you.

Well I spoke to a lady from Customer Response Team based in the Phillipines I think based on the 632 area code I saw in CallerId. Anyway when i asked her if I can talk to her supervisor, she said she is a supervisor and she cannot transfer me over!
Anyway. I called again yesterday and some guy in TechSupport told me he will assign it to a different person and hopefully my experience would be better! We'll see what happens..