I tried upgrading to 4.0 from 3.1.3 jailbreak from the official itunes download. When I do this, it gets stuck really close to completion. The status bar has a little bit left to go and it doesn't budge. I have read another person with this problem and he says to upgrade from a mac, I can't do that currently. Is there anyway around this? I've attempted to downgrade to 3.1.3 but I get the 3194. What can I do right now?