Hi,
I have an iPhone 3G. Everything was working fine until last night when I applied the 3.1 update. I am using iTunes 9.
The update downloads fine, but then hangs when the iPhone tries to reboot to apply the patch. It always returns the error "Unknown (2006)". The iPhone is connected directly to the Macbook Pro.
I called Apple Support and talked to 2 representatives. They advised me to try again at a later time, after we exhausted re-installing iTunes 9, rebooting the computer, trying another computer etc.
After many, many, frustrating tries with this at later times (with the same error), I downloaded the 3.0.1 firmware from:
http://theiphonewiki.com/wiki/index.php?title=Firmware
...and did a successful downgrade. It took 90+ mins for me to restore everything to the state that the phone was at before the crash. This was 14 hours after the initial fracas.
After having read through multiple forums, I decided to try to update again. To no avail. Again, "Unknown 2006".
I am giving up and staying with 3.0.1 until Apple figures out what is happening.
The most frustrating thing of all: I updated my wife's iPhone 3GS in parallel to the update that I made on mine, and hers works fine!!!
Apple, please get your act together!