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In case Apple Staff reads these posts here is what happened with me:
Both my iPad and iPhone 4.0 were connected to iTunes.
First I updated my iPad.
The Update completed successfully.
Then I tried to update my iPhone.
In that very moment a new release of iTunes - 10.2.1 was announced.
So I got “Unknown Error 9” message.
I Installed that new release, but the software said I had to restore back Ios 4.2.1 and only then continue with the installation of iOS4.3.
But the latter cannot be achieved because every attempt finishes with “Unknown Error 9”
So guys find ASAP solution, because the old advices don’t work in this case and because probably a huge number of people all over the world cannot use their phones now.
Windows XP Pro

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