iPhone Not Syncing to iTunes, despite re-install

Hi,

I was having problems with iTunes on a Mac recognising iPhone, iPad, etc. Had tried all suggested fixes and eventually re-installed iTiunes (and removed various pref files, which solved the problem. HOWEVER, a day later the problem has returned.

Does anyone have any tips what is causing this and how to fix it. Separately, my girlfriends Windows PC is not recognising her iPod either. I thought it was just my machine playing up.

Thks