Here is a fix if you run into any or all of these errors while upgrading to 6.1.

Phone Download Fail
PDA Download Fail
EBoot Download Fail

If you get any of these errors you will find that no matter how many times you soft or hard reset it comes right back to the same error messages. This obviously may cause you to think your phone is bricked. Don't worry, it isn't.
To fix this all you need to do is boot the phone in "Pass" mode. To do this simply hold the CLR key (the one between the two softkeys) while doing a soft reset. You will see the word Pass appear on your screen and after a minute the phone will procede to boot all the way. Now simply re-run your 6.1upgrade and it will complete successfully. I have successfully upgraded 3 different i760s that experienced this problem and they are all now working perfectly.

EDIT: Sorry, somehow I missed it in my search but this solution was already posted here. http://pdaphonehome.com/forums/samsu...-out-kind.html

I just thought I would post it here because I spent a very long time on google looking for a solution.