Ive got your solution right here. Im using windows.
So first thing is to: Download the 6.1 file from: http://www.felixbruns.de/iPod/firmware/
And chose the one you want.
The downloaded file will be in a RAR format. So what you want to do before you restore it is:
Go to control panel, then go to the search bar at the top right(windows 7), and type in "Folder"
You should then see a folder icon that says "Folder Option", click it.
Click on the "View Tab", and scroll down until you see: "Hide extensions for known file types" Make sure its NOT checked.
click OK, Then go back to your file and click on it to rename it. Remove the .ZIP and put .IPSW. it should change the icon
Go into itunes and press "SHIFT" + CLICK and it should open the explorer. Find the .IPSW file and voila!
I really hope this worls for you guys! it did for me!!