Yesterday I testet a lot on my device. Suddenly I get this error message when I hit Build & Go in Xcode. First, it asks me if it\'s ok to sign with my key. I click yes,
I was going to mention that dev certs eventually expire, until I saw you mention "My Apple Dev Enrollment is brand new."
Posting anyway in case it helps others... If your setup stops working out of the blue, you may have to download fresh certificates.
if the ipod is brand new u have to check the (use for development) option in organiser
I've had this happen before as well. I'm not sure what caused it either, but in most instances powering the phone off and back on again solved the problem.
So, the final solution to that problem:
If not, go download it from the iPhone Developer Program website
Device power off (really off...you do that by holding that big standby button pressed for a few seconds)
Quit Xcode (quit really: Check in Dock that it's not running)
Activate device (power on), wait until it's bootet completely
Plugin to your mac
Wait until that harrying iTunes starts automatically, wait until it has synched your iPhone / iPod touch, and then switch iTunes off (really off).
Start Xcode
Build & Go
Pray & have fun (hopefully)