iOS4.1 Pre-Jailbroken Base for iPhone 3G is broken. (That's what Brian told me too)
I tried to install 3 times. All failed. I don't know why. It used to work for me but not anymore. After I used WD6, I can't upgrade or restore to it.
How can the exact same file work then get broken suddenly?

There must be an other variable you did not catch yet.
1- On top of which iOS did you try to install it?
2- Did you use the free
iREB to put it in PWNED DFU Mode before opening iTunes and update the firmware?

3- When you say "All failed" what do you mean exactly? Did you get any iTunes error numbers?