We previously reported problems syncing iPhones after updating to iTunes 8.0.1. The most common error message is as follows: "an unknown error 13014." Users reported similar issues with the iPod touch. In some cases, simply restarting the host computer and restarting the iPhone can resolve this issue. In other cases, this procedure is unsuccessful.
A simpler fix that has worked for many users is as follows: Quit iTunes on the host computer, then turn off the device (iPhone or iPod touch) and reconnect it to the host system.