Don't know man, sorry. I think flashing is the quickest way to get things right again. I too had a few strange problems. One flash, and my precious N9 is back on track again!

i tired flashing, well actually not exactly flashing i had a backup image of rootfs and i tried restoring it, it works, everything back to normal.
But i had setup a lot of stuff and configured many things, i really don't wanna go through all that again. The backup is very old and has almost nothing installed.

I have the same problem since ~ 2-3 month:
- not able to autoconnect to wifi
- old connection worked well (until I did't tried edit to test) but any new one don't.
- not depend on the wifi type...tried many, even a pure unencrypted wifi.
- be able to connect with manual connection, so the settings must be proper...
- to find the solution I fumbled my wife's unused N9 from the drawer...but get the same symptoms! :/
- reflash not solved the problem! :/
- at first time when switch to auto mode, it try connect and for 1 moment it seemed woking but than fall back to manual mode.
So I checked my AP-s log: http://pastebin.com/twDVVL5F -> If I have right, the n9 drop the connection, but I don't know why :/

I have no other idea... If anybody has, please share with me/us! Thanks in advance.

I don't think it is the same problem.
Try adding this line to your /etc/hosts file
and recreate your connections:

213.128.137.20 connectivity-test.ext.nokia.com

more on the topic here: http://talk.maemo.org/showthread.php?t=96282

big thanks! Its working!

How did you guys figured that out... amazing. It works like a charm!