[Downgrade] any successful downgrade from beta 3 to 2.2.1?

When i try to downgrade, i can get into system. But it will never activate?

anyone else have any luck?

I had a lot of trouble with this, and iTunes rejecting the restore but I got it to work .
Just DFU, and then restore a clean (not custom) firmware for 2.x.
I may have gone back to 2.1 rather than 2.2 - can't remember.
Then upgrade to 2.2.1 clean.

If you are trying to get it unlocked too, then it's more tricky. You will need to restore, then when it gets to the point where it says your SIM is not accepted, close iTunes and use QuickPwn to clear the lock.
After that - you should be able to upgrade to whatever you need.

Thanks for quick repsonse; however, this did not work for me. just gets me into the phone like before and keeps searching for signal, no service,etc. upgraded back to beta 3 and everything works fine.

Iphone 2G or 3g ?
With a 2g you can downgrade to 1.1.4 with 7.5 itunes afaik (you will get some errors e.g. 1011, 1013, 1015). Cause of the errors the phone stays in recovery mode. You can use iLberty+ to get it out.

Next step is to downgrade the baseband. you can use KiPhone for this. (check downgrade and debug)

After this you can run iLib+ again to jailbreak/unlock. And finally upgrade to 2.2.1 JB. (Need itunes 8 for this)

All this works on Win. Not sure which tools should be used on a Mac. Also unsure how to do with a iphone3g