Hi, I just bought a BlackBerry Curve 8900 unlocked when I setup Wi-Fi connection it says ok but I can't connect (DHCP)to the internet.When I run Wi-Fi diagnostic tool "local IP adress is empty and and for status it says IP adress no longer valid.

Does your carrier require a BB data plan? In many cases, carriers require BB data and the proper service books before allowing WiFi access.

If the device was on BES previously, there could be an IT policy blocking it as well.

Thanks for the answer my carrier don't require BB data plan. I have no idea if the device was on BES previously but when I downloaded a new OS 5.0.0.681 it unlocked by itself but a message came from O2 Germany carrier (I live in different country) suggesting to visit their online site .

A phone does not "unlock by itself" when you download a new OS.
To unlock it, it requires a unlock code.

As for the problem, try rebooting your router.
Or if you have MAC filtering enabled, make sure you enter the WAN MAC address of your BB into the router's settings to allow connection.

I don't have MAC filtering enabled and I have restarted modem also but no success.
Don't now much about a blackberry phones because for a long time I used Iphone but when I bought the blackberry phone it had a OS 4.6 and I install a OS 5.0.0.681 after rebooting it was unlocked don't know why and I could use it with my carrier.

Again, updating the OS will NOT unlock a phone for use on another carrier.
It must have ALWAYS been unlocked.

Thanks so much! It was the Data Services being disabled. Wifi is now working.