You are jailbroken right? Download TinyUmbrella here, install it, open it, and then under "Connected Devices", click your iPhone 4S. Click on the "Advanced Tab" Then uncheck the box that says "Set Hosts to Cydia on Exit"
If it doesn't work, try changing the USB cord, a different user account, or a different computer.
Hope this helps!
PM me if you need help.