Connecting Unlocked/Jailbroken 2G iPhone

[ABigGatorsFan]

I am trying to connect my girlfriends old 2G iPhone to her iTunes account. She has not had it connected and working to iTunes since February (she was using a Blackberry). The phone is Unlocked and Jailbroken. She pulled up her iTunes and is able to use her iPod but when she connects her iPhone it says an unknown error has occured and it won't recognize the phone. She has never updated the iPhone (it doesn't even have the App store). Does she need to download a specific older version of iTunes, or is there some other steps she can take? Any information you could provide me would be awesome; she has been hounding me about it for more than a week. This is my last resort. Thank you.