Guys, solution found!
I remember someone once said, he wiped out the phone, and 3G started working. Now, there is no such thing as "wipe out", but now I think I know what he meant, AND IT WORKED FOR ME.
After upgrading to android 2.2, reset your phone to factory settings, settings->privacy-> factory data reset.That's it. Beware that u will lose some info, like installed apps.
hope, it works for u too.
