iphone 5 will not synch, itunes stops responding
I have had my iphone 5 for over a year. In the last month when I plug it in, itunes will freeze up and stop responding. I can not synch, add new music, new movies. I have to shut down itunes. This happens whether I plug in my iphone or my husband's iphone (both iphone 5's). Without an iphone plugged in, itunes will not freeze. My iPad air synchs just fine.
We have shut down the computer, we have tried numerous times. All software is up to date. Itunes is running 11.2.0.115. The iphones are running iOS 7.1.1. This was happening on iOS 7.1 but I don't believe it was happening before that update.
Any ideas?
iPhone 5, iOS 7.1.1