I was attempting to update my OS4.1 BB 6.15.00 3GS to 5.0.1, but it failed.
I used the latest Redsn0w to make a custom firmware to preserve the BB, then used Redsn0w again to boot into Pwned DFU. I then went into the latest iTunes and restored with the NO_BB custom firmware. It went through the normal update process, but when the iPhone rebooted after restore, iTunes informed me that it was still in recovery mode.
When I try to re-restore, I get a 1600 error unless use iReb to get back into pwned DFU. I tried making a custom 4.3.3 with redsn0w and restoring to that, but I got the same problem. I then tried the custom 5.0.1 again. Still not working. I searched a bit on the forums, but couldn't find anything.

Here's a link to the first update log (pastebin)

Anyone have any suggestions?

Thanks in advance!

bump because I still can't figure out a solution.
thanks.

When you get the 16xx error, does TinyUmbrella work to 'kick device out of recovery'?

Sorry for the late reply, but TinyUmbrella didn't work.

I've made some "progress" though.
I'm technically at 5.1 (got there with pwned DFU + custom no bb fw), at what should be a tethered boot. The installation through iTunes goes fine with no errors, but after the FW is done installing, the phone goes straight back into DFU mode. When I boot tethered with redsn0w, I see the pineapple logo, then the apple, then the spinning circular loading bar. Then it shuts down and goes into DFU according to iTunes.

When I attempt to fix recovery with redsn0w, I see everything come up on my phone, then I see the walking pineapple for a split second, then straight back into DFU.

I tried unlocking with redsn0w just to see if it would work. It goes through all the linux prompts and then the walking pineapple loading screen. Everything seems successful, but then it goes back into DFU.

Anyone got anything?