I'm one of the unlucky ones who got "no signal" on their 3.0 iPhone 3G It's been 6 days since ultrasnow got released, and after doing everything I could, I decided to go back to 2.2.1 ..

Can someone please tell me what do I have to do, in order to downgrade my iPhone ?? Should I just make a custom 2.2.1 firmware and restore the phone, or will there be problems ??

You really can't because in order to go back to firmware 2.1.1 your baseband will also need to be downloaded to the correct version.

Unfortunately, downgrading the Baseband on iphone 3G is possible if and only if you have BB bootloader version 5.8 (very early iphone 3g).

Even if you can downgrade the baseband, what good is that going to do because yellowsnow deos not work with BB in 2.2.1 firmware.

The only logical downgrade is 2.2.0.