Tried your method but when i try to connect to WiFi it says "Can't Authenticate"

How can i solve this?

Impossible to say, have you been able to connect to your wifi network before? Are you using correct credentials and security settings? It's impossible to tell exactly what is wrong with the info you provided.

WiFi worked till this morning. After i entered the following in the terminal after that started having this problem.

gconftool --recursive-unset /system/http_proxy
gconftool --recursive-unset /system/proxy
gconftool --recursive-unset /system/osso

I'm using the correct key to login. But still it refuses..

All I can say is that you should've read that thread...
Work you way up from the less drastic workarounds, to the more drastic ones.
But it sounds like it may all be moot now, might need to jump to re-flash etc.

Still cannot connect..

Is it possible to download the Fb application for N9?

I have another solution found for the "cannot connect to Twitter/Gmail/Facebook/whatever" problem which can be used without Dev-Mode. In my case it seems to be all about the proxy settings. After using my work WiFi (which needs proxy) switching back to mobile data connection (where naturally no proxy is configured) seems to forget sometimes to "unset" the proxy configuration.

So I could use 'gconftool --recursive-unset /system/proxy' and 'gconftool --recursive-unset /system/http_proxy' and am good to go... But I didn't want this to do every other day...

So I just set the proxy config for my Mobile Data connection from "No Proxy" to "Manual", but leaving the proxy address fields blank (as they are, no changes) in the connection's Advanced Settings.

The following now happens: After switching the connection from my proxy-needing work WiFi to mobile data, the values in /system/proxy and /system/http_proxy no longer get deleted, but are just set to empty values. And with empty values the system actually assumes (what is correctly intended in this case) that it should use no proxy.

This worked for me so far. Try it! You don't have to enable Dev-Mode for this.

About the Wi-Fi connecting problem however I don't know, for this issue we should look at another configuration place?

I wonder if this is why everyone's getting this or if there's other root causes?
Either way excellent workaround for this particular issue, I will add it to the guide!

Thank-you.

The FB and GTalk has been working fine until today.
Sometimes, in the Availability page, they consistently showed me "Incorrect Password" even after a few tries to set to "Online".
I switched fro and back from mobile and wifi and they work again
(I don't use proxy in any connection)

Other Skype, MSN and Yahoo I'm running are doiing fine.