iPhone isnt recognized by computer or iTunes anymore. 3G

For some reason, I now cant sync my iPhone with iTunes. This also applies to the other apple products I have, which is two iPod Touchs and an iPod Nano. I synced my iPhone and then a few minutes later I was going to sync my daughers iPod Touch and thats when my computer quit recognizing anything thats plugged up. Does anyone have a clue what could cause this?

I googled this topic and Ive done all the trouble shooting you can do. My computer simply wont recognize any device anymore. Ive never had this happen before, so Im at a lost right now on what to do.
Acer Windows XP