I'm having the same problem with my 3G.
I pwnd successfully, but when I modified the mobile installation file, and added the Documents folder, with the correct permissions, it got stuck on the apple logo, on reboot and now vibrates twice and tries to reboot. Attempts to restore keep getting the 1600 or 1601 errors
Update: I was able to restore but not sure how I got the phone to do so. I did try to boot the phone into DFU mode - I had a black screen for several restore attempts. After trying to enter DFU mode - I couldn't get I tunes to recognise a phone in recovery mode. I plugged in the cord holding down on the home button and finally got the restore screen graphic. I restored it with the firmware update and will pwn it again, later.
Curious to know if anyone had trouble after modding the mobile installation file.