iOS4 on 3GS - No WiFi

I compared with iPod touch DHCP (still 3.1.3) against iPhone 3G iOS4 DHCP.
It is
iPod touch: DHCP Request / DHCP ACK
iPhone: DHCP Discover / DHCP Offer and then nothing more.
Need to read and think about it (tomorrow).

I have the same problem.

After upgrading to iOS 4.0 last night, the option for wifi is greyed out! :@

Anyone found out what the problem is and more importantly how to fix it?

Put me in the same boat... Updated today to iOS4 and all is well except no Wi-Fi... In the settings it says it's connected but I'm not seeing the indicator in the top of the screen next to the ATT signal... Only shows 3G which is taxing the battery, of course. Any suggestions on how to fix this wold be greatly appreciated.

I'm not seeing any wifi icon on my 3GS having upgraded to OS 4.0 a few hours ago. I have an iPod Touch which I have not upgraded and it has no problems - full wifi bars.

I've tried rebooting my Airport, restarting the phone, switching WIFI modes on Airport - no luck.

I notice that the settings for my network are not the same when comparing the 3GS and the Touch - they are both DHCP but whereas the Touch has values in IP Address, Subnet Mask, Router and DNS, the 3GS only has values in IP Address and Subnet Mask and they keep disappearing and reappearing when you are actually looking at the screen! The Touch values do not keep disappearing.

Not sure how all this stuff works really but one more thing: the IP Address on the Touch is 192.168.0.6 (fairly standard) whereas the 3GS is showing one that starts 168.254...

Apple - there is something wrong somewhere...

JW64 ... you are correct ... generally speaking, the IP address needs to be 192.168.0.xx ... if it's anything than that, you're likely not going to get anything.

Something is definitely screwy with iPod Touch 2G and WiFi, because it is terribly inconsistent in either iOS 3 and now iOS 4.

Good thing it's just a toy for me ... as I am using my iPad all the time.

And NO, the iPad is NOT a large iPod Touch ... for the BILLIONth time.

Well it seems the 169.254... address on my 3GS might explained by this article:

http://support.apple.com/kb/ta26003

I have no idea what it all means though! Nor why my Touch should have a different IP when it is connecting to the same Airport.

All I know and care about is that the wifi on my 3GS no longer works in my own home. Marvelous. Not.

A post on Macworld's forums claimed that Apple support said iOS 4 doesn't work with WPA 2 security at the present time. That's what I have on my home network so I guess I'll just wait a while before upgrading my iPhone 3Gs

My wifi all of a sudden got grayed out. It was working great all day and then all of a sudden the wifi stopped working. I did a soft reset on the iPod and then when it came back up it said to plug into itunes. So I did that and then it had to restore the entire thing (60gb of data). When it finished I went to use the ipod and no wifi. I went to the settings and the wifi tab is grayed out. I go to general and bluetooth is also grayed out so I went to reset and reset network settings and still no help. Just wondering if anyone is having this problem.

So if it doesn't work with WPA2 security, which is what I'm running, then that would explain it, since it works on everyone else's NON-secure networks.

BUT ... I JUST now tried something, and it here is the RESULT.

I just went into AirPort Utility and changed it over to WEP 128 bit (whatever that means) and it WORKED.

Does THAT make any sense to you? It's doesn't to me, but if someone can explain it, I would certainly appreciate the additional insight.

I was wrong yesterday. With iOS4 it is Discover / Offer / Request but then it is my fritz.box not acknowledging the request.

Wifi is greyed out on my 3G after the update, have restored it from Itunes, still dead inactive. Trying a reset from the phone itself now.

Posted Yesterday, 11:50 AM
Solution found:

With the aid of Apple tech support I learned that iPhone iOS 4 is INCOMPATIBLE with WPA2 network security!!!

Downgrading my network's security to WEP restored wifi to my iphone.

I consider this a shocking deficiency in the new iOS, but the Apple tech assured me they would fix it with an update.

http://forums.macworld.com/index.php?/topic/127340-upgraded-3gs-to-ios-4-lost-wi fi/

Tried downgrading network to WEP, no joy - my wireless on the iPhone 3G is greyed out

If your wifi is greyed out and says "No WiFi" then that has nothing to do with your Access point configuration.

If you are able to scan for your wifi network, connect to it, but see a 169 address, try rebooting your access point (i.e. pull the plug for 10 seconds and re-plug). I have WPA2 and it works fine for me.