Arduino Nano 3 not recognized when plugged in before PC bootup

We use the Arduino Nano 3 for sensor input. This board is always connected with a usb cable. The problem we are facing is that it is not recognized if it is already plugged in when the computer is turned on. Windows (vista & 7) recognizes it as an unknown device. What can we do to make the Arduino work in this setting?

This issue has been raised before by someone else but no solution was found.

The workaround we have is to put a powered USB hub between the computer and the Arduino Nano 3. We would like to get rid of this hub, because it is a hassle and does not look nice in our final product.