Strange WiFi problem on iPhone 3G after 3.0 update

Ryan, I tried all 12 channels (exciting exercise) - no cigar.

After each channel change, did you reset the network settings on the iPhone? Try that... I know the channel change was the trick... Man was I upset when I first got this software... It wouldn't connect and the times it would connect, it would be super slow. I haven't had one single problem since changing the channel to manual. Not sure exactly how that would affect it, but it did... Could be too much wireless interference that the iPhone couldn't pick up the signal...

well nothing seems to be helping with regards to this WI-FI problem so I'm booked in to see a 'Genius' at a localish store. Wish me luck!

I restored mine and started it as a new iphone on itunes (i didn't restore my old settings) and it worked for a day. Then I installed something else...and it got messed up again...i tried restoring it like i did before (when I got the wifi to work properly) and now it can't find the wifi networks again....argh! Apple better fix this in 3.1!

is there anyone who returned his/her iPhone for repairs/replacement without any warrenty left?
I just checkt and found out that I have no warrenty 😟
if this is a hardware issue after all (which I still doubt), how much would it cost to replace the wifi-unit?

I had wifi for 10 minutes after my first restore, but that has been 2 weeks ago and I haven't had wifi since, even with the second and third restore attempt so I fear the worst

Ok - I've had the issue with the iphone connecting to my router but not allowing me to connect to internet etc.over wifi. I have a Netgear router (Sky Broadband) and have just got my wifi working again - here's what I did.
Asked iphone to forget network - found my network again - used a static ip - accessed my Netgear Router and in 'LAN IP Set up' I assigned my iphone an ip address. Then turned off wifi on the iphone and turned it back on again. Wifi is now working fine!

Hope it lasts!!

I recommend you to check with jason@ithinkitsbroken.com - He is the most skilled iPhone engineer - Period. He's also the preferred hardware engineer for the iPhone community, besides he won't rip you off. You can chat with him on the Hackingt0sh IRC: irc.osx86.hu - #iphone (nick: ctrlfreq)

If you want to read how I fixed my iPhone 3G wifi:
http://dreezrulez.com/iphonewifi.htm

Think my phone had a slightly different problem to most others, where I could connect to the wifi, but it dropped out and then tried reconnecting virtually straight away, but didn't load all the data on a website for example.

Took my 2nd iPhone to a Genius Store in Bristol and exchanged it for another phone (60mile round trip so better not mess up again). So far so good. Wifi is working and I can now use my car charger too!! Have set the phone up as a new device rather than restore. If this goes wrong again, I will back!

Ok
There is so much content in this thread that I don't know what has been done.
Can anyone give me a quick summary of any/all of the solutions to the original problem.
Shame you can't just go straight to it :/

Here's a summary of what has been advised (I've tried it all 😉 ):
1) turn off push email
2) turn bluetooth off
3) if you can see your network in the list but it doesn't connect, press the little blue arrow and press 'renew dhcp lease', or 'forget this network'
4) forget network settings: settings>general>reset>reset network settings
5) forget all settings: settings>general>reset>reset all settings
6) restore: itunes>restore (it wil replace your 3.0 firmware with 3.0
7) setup as a new phone in iTunes
8) change wifi router to 'G only' rather than 'mixed' or N protocol
9) remove your wireless security, set it to 'none'
10) set your wifi security to wpa2
11) change your wifi channel to 1, 6 or 11 which are most common, or just change it to any random number which has helped for some people
12) upgrade the firmware of your wifi router/accesspoint
13) put your iphone in airplane mode, than put wifi on
14) turn bluetooth on for a short amount of time so the chip will get accessed
15) remove your simcard
16) keep pressing 'refresh' in safari until it askes you to connect to a network
17)downgrade to 1.4 with the correct baseband, than upgrade to 2.2.1 (which voids warrenty)
18) wait for 3.1 which MIGHT fix this 😉

I tried to make the list in proper order, but there is no solution for everybody yet. If none of this works, you can wait for 3.1 or get a new phone at the local genius bar which might just be a temporary fix. Hope this helps

Wow!
Thanks that's really super useful!
I have done a full reset but it has gone all wrong and is stuck at the Apple logo so will have to put it in DFU Mode.
Why is nothing simple!? :@

Anyway, thanks for that really comprehensive list.
Joe.

I had that same issue when I did the full reset (when you remove all media too right?) and I had that same apple logo
Go to DFU mode and then restore in iTunes, works fine after that, without the wifi that is.. 😟

Hi All
Results...
After having terrible problems resetting. I put it in DFU Mode, deleted all my back ups and re-downloaded OS 3.
So a completely fresh start, and speed wise its great, nice low(er) PINGs and decent speeds.
Although, it kept disconnecting me and re-asking for the password. So I have set up a static IP on my device which so far seems to have stopped those problems.
However, my hateful Belkin N+ Router isn't shwowing my device on the client list.
But thats more minor, but I hate the router so much, I want my old Netgear DG834N back which I will probably do.
Anyhow, I will jailbreak now to see if that makes any difference and then unlock and continue testing.
My advice for all my equipment, is if you have a problem you can't solve, go back to as close to square one as you can.
No back ups, fresh downloads of the updates etc etc.

Good luck and will post any further details as and when!

Spoke too soon...
Back to its old ways again.
So annoyed and angry.
My only other option now is to replace the router and see if that makes a difference.

Guys, plz stop wasting your (and our) time with changing things not related to the iPhone.
I is the freaking phone, nothing else. Even if switching to another channel or router makes a difference - it will not solve the problem.