iTunes uses iSync to transfer files to and from the iPhone. Naturally, iSync keeps track what files have been copied where. Previously I had used Address Book for family, friends and business associates info. As Eudora was showing its age in Leopard, I moved this list to Address Book, but did not want to copy them to the iPhone. Family was already in a group, and you can sync any groups or all. I created a new group and dragged all those I wanted into the group. I opened iTunes with my iPhone connected and sync info, selecting family and the new group. The friends and business associates were already on the iPhone, but not in a group. You can access names on the iPhone by name or group. After syncing, all the names were in my iPhone only the friends and associates were without any telephone or email information, totally blank. I deleted all those from the iPhone and again sync with iTunes. Now the Sync warned me proceeding would delete all in the new group on the Mac. First Sync “knew” it had already sync to the iPhone, now it would sync the changes it found in iPhone to the Mac and that group was empty. I cancelled the sync and scratched my head. Realizing the warning window was a iSync dialog window, I opened iSync In iSync’s preferences is a button label “Reset Sync History”. I realized this was the solution, tell iSync to forget everything. I again told iTunes to sync my info and everything was soon as it should be.