I am not totally sure what you mean by "crack/flash" but if you are trying to use your AT&T 8300 on USCC, I doubt you can because AT&T is a GSM carrier and USCC is CDMA. I am also wih USCC and I tried to take a Verizon phone (which is also Cdma) in and get it activated and that didn't even work. The only curve model that works for USCC is the 8330. Hope that helps!
Posted from my CrackBerry at wapforums.crackberry.com