Problem in activating device..

Hi all..

I was using my iPOd touch for dev purpose for past months..
I changed my Mac computer, i restored my device with OS2.0 again in Xcode.

Then i sync ed it with iTunes, still Xcode is telling me to activate the device...
I selected "Set up a new device" rather than storing the backup" in iTunes.
Why so?

I am using iTunes 8.0 (is there anything like iTunes 8.0 can used to activate OS2.1 or above??)
I am using OS2.0 .

I restrated the deivce, quitted/oipened Xcode/iTunes etc.. no change..
Please help..