Wi-Fi stops working after updated firmware of carrier iPhone

Hi all,
Here is my device info: iPhone 4, iOS 4.1, Carrier Three Australia (unlocked).
I was updating a few applications through 3G signal when I saw a prompt on my phone asking me to update the carrier firmware. So I did. The phone just stopped downloading for the applications and could not be paused.
Things seemed to be alright after a reboot, until I found out the problem of the Wi-Fi connection. It ticks the wifi connection which is listed in the wifi networks, but there is still a 3G symbol besides the signal bar. When I turn on the Airplane Mode and use the Wifi only, the wifi symbol wont come up and there is no connection at all.
I tried everything, rebooting, resetting, restoring and renewing the lease, none of them helped.
Does anyone know why is that happening and how to fix it? I am literally running out of my data usage...
iPhone 4 iOS 4