I had this problem as well, but got it to work this morning. I dunno if it makes a difference but I'm using a MBP.
I connected the phone, opened iTunes manually, went to the summary page for the phone, unchecked "Automatically sync when this iPhone is connected", clicked "Apply" and then closed iTunes completely. I did NOT disconnect the phone. I reopened iTunes manually, went to the summary page for the phone, checked "Automatically sync when this iPhone is connected" and clicked "Apply". It then said it had to start the iTunes Helper Program for this since it wasn't currently running. I said OK.
It now opens iTunes automatically when the iPhone is connected.