I've just used Ultrasn0w to unlock unsuccessfully, but I think it's because I left my standard O2 iPhone SIM in when I did it. Two questions -

1. To redo it do I need to restore the phone and run Redsn0w again, or can I just rerun Ultrasn0w ?

2. If I unlock for a given SIM can I then change the SIM for another one ?

redsn0w decides whether to hacktivates a phone or let apple's activation run based on the sim card inserted at the time redsn0w is run.

For official sim card carriers, redsn0w only jailbreaks and lets the phone activate normally via itunes.

For non official carriers, redsn0w jailbreaks and hacktivates.

You need to insert the sim card you actually want to use with the phone and run redsn0w again (not sure if this will work)

If that does not work, u need to restore iphone and then run redsn0w with the correct sim card inserted.

Once you are hacktivated you can install ultrasn0w from cydia if you require this for unlock.

Just to clarify, can I actually use any non-approved SIM initially and then change to the one I really want later, just as long as I start with one that is not an official one. Problem is I am not going to have the target SIM until I arrive in the country I am traveling to and then it is too late to do the unlocking.

I think I read your original post incorrectly.

Just so you are clear on the terminology:
activation: get past the "connect to itunes screen" so you can actually use the iPhone. Also enables youtube access and push notifications.
unlock: bypass carrier lock set in iPhone to allow non official SIM cards to be used to make and receive calls.

Activation on the 3G or 3Gs is actually a wildcard activation. This means that you can switch SIM cards and you do not need to reactivate. For non o2 SIMs, you still need ultrasn0w for unlock, as your phone will operate like an iPod touch (no ability to make phone calls) until you load ultrasn0w to bypass the carrier lock.

If you have a valid o2 sim that can activate the phone with itunes, Redsn0w will just jailbreak and install cydia but skip hacktivation...
It sounds like you have done the right thing and simply need to uninstall or disable ultrasn0w until you travel to the other country where you can install or enable ultrasn0w and use the foreign SIM.
I would recommend though that you test this before you leave your home country, you just need to test with a SIM card from another carrier and ultrasn0w enabled.

Thanks, will do.

Now all sorted thanks. I didn't need to restore, just re-ran Redsn0w - didn't even need to re-run Ultrasn0w. Just tested it with an Orange SIM, working fine.

It's very good that your problem is solved so easily. So you did not re-run Ultrasn0w? Or did not any reset? Just changing sim your problem solved? Strange!

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