Why when I restore my iPhone, the error 3194 stops the restoration?

Renato, try the trick from here I tells you that this is due to Apple no longer signing the version OS 4.00 anymore

"we can bypass this signature checking when iTunes contacting Apple by changing the server from Apple’s Signature Server into Cydia’s clone of Apple Server.

It’s easy (for Windows):

1. Fired up your cmd.exe, and make sure you have administrator privileges.

2. Type this is: CD \WINDOWS\SYSTEM32\DRIVERS\ETC

3. Type this: edit hosts

4. Add this to the last line: 74.208.10.249 gs.apple.com

5. [UPDATE]: Save the file (People asked me to add this, it’s a common knowledge tho when you change a file you must save it)

6. Restart your iTunes.

7. Put your iPhone 3G in recovery mode, by turn off the device first and pull the plug from your PC. Then press Home Button and connect your iPhone into your PC, then wait until the Recovery Icon shows up (iTunes icon with cable above it).

8. Now, restore your iPhone with your firmware iOS 4.0 (in windows using Shift + Restore, in mac using Options + Restore)

9. Voila, it will be restored succesfully, it’s fully working on my iPhone 3G.

You should notice the number 4 step is the bypass server, by pointing Apple Authentication domain into Cydia’s Server IP Address, this is trivial in unix, and thankfully, we can do this in Windows.

On Mac, it’s the same, except for the cmd.exe and the cd thing should be into /etc/hosts…"

Hope this helps, there is more about it on http://techie-buzz.com/mobile-news/iphon... Good Luck