if you cant turn on the phone at all then im afraid you gonna have to exchange it. i hard bricked my phone today while experimenting with ICS leak and wanting to go back to GB stock. the same situation as yours. after digging xda forums for a few hours looks like the only option is to exchange it if you have a warranty. you can try USB jig (look it up on amazon.com) but people report it doesnt help with complete bricks. (if the phone doesnt turn on at all) I wanted to order one. but then simply called to att and will be getting a refurb exchange.
bottom line - dont mess with your expensive device. lesson learned.
yeah i saw their video and equipment they use. luckily, i got my exchange yesterday. so I'm OK now its just i am wondering if you could go back from ICS leak to GB stock.... I managed to get my phone back to GB however the phone application was crashing every time i would tap on it so basically the device was unusable and when I tried to reflash it again through Odin i chose "phone" option instead of "PDA" and that's hard bricked my phone...
Thank you Ronnie I appreciate your help. this is the first time ever i hard briked my device lol used to mess with blackberry os leakes back in the days and it was fun anyway, I find this ICS leak is at beta stage as some things dont work there as they should be. So now I have another issue. stupid ATT sent me an exchange with 2.3.6 and I hate it.. the wallpaper is non scrollable there and there is no way to fix that and the stock browser doesnt have vertical or horizontal fixed scrolling, so its a somewhat messed up update. I was wondering if I can use Odin to flash to 2.3.5 I'm still debating though if I really should bother doing that but just wait for official ICS update... this 2.3.6 doesnt have Carrier IQ on it btw. lol