i just did a similar thing- i had a defective iphone (part of the screen stopped sensing touch) and it had been unlocked/jailbroken with iplus. it was tough to find the answer, but i believe those who say it just needs a restore are missing the issue of the bootloader. what i did and was told to do was to erase the baseband and then restore to 1.1.4 using itunes. i erased the baseband using ziphone 3.0 which has a graphical user interface and allows you just to erase the baseband. it all worked well and the apple store did not find any problems with the defective phone
this is where i got my information. i was not able to get eziphone to erase the baseband so i just used the latest version of ziphone.
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