I have a iPhone 3G. I'm having trouble connecting to my WIFI.

I'm sick. I'm tired. I have tried a lot. The only thing left to do is to fall off a cliff. Please help!!!

Here's what I have tried:

1. WIFI with no security


2. WIFI with WPA security


3. WIFI with WPA2 security


4. router modes
   
   
   1. b&g only
   
   
   2. b&g&n mixed mode
   
   
   


5. turn off 3G


6. turn off data roaming


7. reset network settings


8. reset router


9. restore iPhone (not a clean re-store)

Here are some notes:

1. iPhone 3G firmware version 3.1.3


2. NeatGear N router


3. It used to work before. Not sure what made it stop working


4. WIFI is always found but always get error "unable to connect to network"


5. All laptops are able to connect


6. My friend's iPhone can also connect. His firmware version is 3.1.2


7. My router firmware is up to date

Thanks
Power Ranger