iPhone isn't recognized by computer or iTunes anymore.

For some reason, I now can't sync my iPhone with iTunes. This also applies to the other apple products I have, which is two iPod Touch's and an iPod Nano. I synced my iPhone and then a few minutes later I was going to sync my daugher's iPod Touch and that's when my computer quit recognizing anything that's plugged up. Does anyone have a clue what could cause this?

I googled this topic and I've done all the trouble shooting you can do. My computer simply won't recognize any device anymore. I've never had this happen before, so I'm at a lost right now on what to do.