Yesterday I updated both devices. (iPhone via iTunes, iPad via Air)
Both were capable of accessing the same WLANs befor the update!
the iPad had no problems after all, re-accessing them, but my iPhone4s since then is very picky!
It will only access the WLAN of a Deutsche Telekom Consumer-Speedport-Router, belonging to my father in law.
My own, "professional business" WLAN-Router (LANCOM 1821) can´t be accessed anymore.
I set up a few new different SSIDs with different encryptions, everything between WEP64 and WPA2.
At first I thought it might have to do with the encryption algorythms...but after having tryied all of these, I don´t think so anymore.
Result is always the same, the iPhone cannot connect to the network(s), while the iPad could access each and every single one without problems.
The alternative router, where it can establish a connection is also protected via WPA1/2.
I also tried to "reproduce" the settings and transfered the SSID and passphrase to my office router, copied the exact settings, but this didn´t help either.
I´ve tried every hint, tip and advise, that has been swirling around the net (except the one, where someone says, that You should put Your phone in the freezer for 30 mins. and it will connect again) but nothing has helped so far.
Wether it is reset of networks, turn mobile data off and on again...oh and by the way, for those who give the "clou" of "select Your Network, ignore it and re enter the parameters":
In Order to do so, You have to be connected to a certain network, to drop and ignore it...if You can´t connect to any network anymore, You can´t dismiss it!
I did not change anything in the original setup, which allowed iPad2 and iPhone4s to connect to the same networks.
So my thoughts are more and more down to an "artificially forced" chipset compatibility problem between certain manufacturers, caused by some code lines in the new iOS6 on certain devices.
At this moment this is my most logical thought on why after the update my phone can´t connect to a networks it has been running with ever since.
If anyone has any different ideas or solutions to pinch the iPhone back into the wireless, I´d be very glad to hear about.
with the best regards from Germany