Are you coming from ICS, or Gingerbread? Did you flash the Gingerbread bootloaders by chance?
You could try to find the Froyo bootloaders, use Odin to flash that, and then try to flash the .pit and JFD files to go back to stock. I don't think that should be the problem, but it couldn't hurt. I know you're trying to get back to stock, but you could try to use fishman's odin image for his rom:
http://forum.xda-developers.com/showthread.php?t=1441976
I've used it before, and can verify it's good to go.
Can you get into recovery? You won't have CWR, but I'm just curious if you can even get to the stock Samsung one (like if you were going to root the phone the old fashioned way).