Cannot access wifi on my home wireless network

This seems to be a continuing problem with the iphone; I've had it periodically with the original phone and am having it again with the 3GS. Wifi will work everywhere except on one's home network. Restoring, rebooting, forgetting and joining the network are all listed in many forum posts as possible fixes but none have ever worked for me. Seems that the technology just isn't ready for prime time as Apple never admits the problem, but it mysteriously disappears and reappears at intervals and sometimes coincides with iphone updates. Some updates seem to cause the problem and others seem to fix it; not sure as Apple won't admit there is a problem to begin with. Not the case however as the hundreds of forum posts can attest. Perhaps no one knows how to make this technology reliable.

I am having a similar issue. I had to replace my wireless router and have been unable to remain on WiFi with my 3GS - I can log in, but if I don't continue to use the phone while connected to WiFi, it shifts back to 3G. I have tried the "reset" and am hoping that will do it, but after reading the other post in this thread, I am no longer optimistic...
My husband has the 3G and has not updated the software and is able to remain logged onto WiFi and can also maintain a charge (another issue with the software update). I charged my phone last night, unplugging it at 8 pm, and by 10 am, I was at 20% with minimal use.

Update: 1/2/11

After last post the problem eventually went away and I was able to once again use wifi at home. Now we have added an iTV to the mix and it had the same problem; it could see and identify the airport extreme and connect to it but couldn't get out to the internet. Called tech support and we rebooted both the cable modem and APX and the iTV is now getting out and the iPhone has stopped accessing the APX. The symptoms are the usual, it will identify and join the network but the wifi symbol may or may not appear at the top of the screen. In either case it is not truly hooked up to wifi as any net access is via Edge and the wifi symbol will disappear, if it is showing at all, as soon as you try to link to anything online.
I have tried all the usual methods of getting connected, forgetting the network, turning Airplane mode off and on, same with 3G, etc, rebooting, restored the phone, etc., nothing works. Now, I could reboot the cable modem and APX again but then the iTV would probably quit accessing the net so I am loath to do so. My iphone will connect to wifi everywhere else I try, just not at home. We currently have two macbooks, one windows machine and the iTV which will connect to the internet through the APX, only the iphone is refusing to work. I can't understand why this technology is so poorly implemented as this problem seems endemic to all iphones.