I'm having the same problem. I followed the no-counter-tripping method to flash a root-injected stock ROM and it worked fine.
I flashed to CM9 and the camera wasn't working, so I used Odin to flash back to the same root-injected stock ROM and now it never finishes booting.
I noticed that flashing to the root-injected ROM didn't delete my apps, which seems strange. I suspect that there's something lingering from CM9 that is causing the loop in stock. I don't know any way to wipe the device and flash only the root-injected ROM, but I'm hoping that will fix it. Is there a way?