I updated my iPhone to 3.1.2 as soon as PwnageTool 3.1.4 was released and am using it (jailbroken and unlocked) with my T-Mobile plan with no problems.

My phone has recently been showing the message "This accessory is not made to work with iPhone." Upon further research, I found out that this is a relatively common problem among 3G users, and that if I take the phone to an Apple store, they are familiar enough with the problem that their official policy is to replace the phone on the spot.

With a jailbroken and unlocked iPhone, it might be a little hard to go looking for service in an Apple store. My initial plan was to restore the phone, have a friend of mine (with an official AT&T iPhone) put their SIM card in and go get the phone replaced for me.

If I download Apple's 3.1.2 FW update and restore my phone with that in iTunes, will that then (hopefully) un-jailbreak and re-lock my iPhone? Or will it just brick me.

download latest f/w (if you don't hv). restore once/twice.

I get that message when using my Bose sound dock, I read somewhere it was a change in the charge connections, or voltage (memory is failing). Are you saying its the phone?

Don't forget chances are high that the replacement phone won't be on 3.0 or 3.0.1 since this wouldn't let you unlock your new phone in any way.

I remember to read that Apple advised all Apple Stores to update their replacement phones when 3.1 came out.

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iPhone 3G 16GB 3.0.1 Black T-Mobile D
iPhone 2G 8GB 3.0.1 Vodafone.de
MacBook Pro 15" Early '08 2,4Ghz