Problem transferring from OS 10.4 to OS 10.6

OK, here's a problem I posted on a couple of weeks ago, and got not a single reply.

I have recently upgraded from a G5 PowerMac running OS10.4 to a MacPro running OS 10.6.

When I tried to sync my iphone with the MacPro for the first time, it refused to do so (error 13019). In the end the only solution was to do a full reset on the phone, and this cured the problem. My iphone now syncs with my MacPro. BUT, I have lost all the information on my iphone eg 2 years worth of SMS messages and photos (or at least the ones I hadn't backed up to my computer).

So I went back to my PowerMac and tried to restore from that. Of course, it can't; my iphone is now running a version of the IOS that is incompatible with the version of itunes that runs on the G5, so the G5 no longer recognises the iphone. And the G5/OS10.4 combo can't update to the relevant version of itunes.

So here's the question: how do I recover the backup information on my G5 and restore it to my iphone? Or, if this isn't possible, is there a way to access the restore information on the G5 as, for eg, a text file?

Thanks very much for your patience.

J