IOS 4.2 - WiFi finally working again ... and then not :(

Question

There's many reports of users losing WiFi with iOS 4, including me
My perception is that things went wrong with iOS 4 after Apple `fixed` the +signal-strength bug+ for iPhone4 in +iOS 4.1+ ... that's when WiFi-trouble began for me anyways.
I had almost given up on WiFi for my iPhone (d* Apple), until ... this morning I installed +iOS 4.2+ and found WiFi +temporarilly working again+ ... with some trouble.
- All surrounding networks were instantly found when WiFi was enabled again on my phone
- Logging in failed two times, but 3 was my lucky number
- Internet over WiFi: no problem
- An hour later, when I had left home and came to work, al was as it was before; no WiFi-networks to be found
- Back at home in the evening; same thing ... back to bottoms; no WiFi
It beats me why I had this shortlived pleasure of WiFi, and why it was taken from me again.
+Anybody else had this, or has ideas?+
Besides that disappointment, my *battery had completely emptied* in eight hours time without me actively using it (3G on, no phone-calls made, no roaming) like it has done since iOS 4.1 when WiFi was enabled, but unable to find any networks (and trying... and trying...). It must cost a lot of battery (processor?) to find WiFi networks. Maybe the quality of my battery influences all this? (1,5 years old...).
Also *problematic signal* from my provider (T-Mobile - NL) makes my phone switch constantly between 2g an 3g.
I'm somewhat suspecting this issue is overall due to combinations of four:
+poor battery+,
+poor processor strength+,
+poor signal+, and
+poor software+.
Does this ring bells with anyone?

Answer 1

I don't know what precisely causes losing WiFi. Many people have this with different symptoms and some with different solutions. So the cause can hardly be unique for all of them. Some descriptions of what people have reported:
- not finding networks at all (like I have)
- finding networks, but being unable to login at all
- finding networks, and being able to login after repeatedly trying
- being connected, but not having the WiFi-icon
- being connected with icon, but still having Internet over 3G
- being connected with icon, but losing WiFi after some time again (like I had after upgrading iOS 4.1 to 4.2)
- and maybe I forgot some...
Some solve it by changing their router-settings (b/g/n/a, MTU, CTR/RTS, WEP/WPA(2)/none, ...), some just restart the router, others go back to iOS 3 and have success and the +daring few+ re-flow their iPhone-motherboard by baking it in the oven (that's the only one I haven't tried ).
But most people just stay stuck without WiFi since iOS4.
The various success-stories indicate that the cause of this problem cannot be due to some single failure; IMO it must be a combination of unpleasantries that started with something bad in iOS 4 with some other circumstance(s) adding up to a phone not being able to WiFi.
What all of us have in common is that it worked without a problem on an iPhone 3G/3Gs untill iOS 4 was fixed for the iPhone 4. At least I haven't found reports of WiFi-problems with betas and the initial release of iOS4.
Just my 10 cents, but join in with our 10 cents we might figure out what actually happened here.