USB 2.0 high-speed devices are recognized as full-speed after you hibernate and then resume a computer that is running Windows Vista or Windows Server 2008
Assume you connect a high-speed USB 2.0 device to a computer that is running Windows Vista or Windows Server 2008. After you put the computer into hibernation and then resume the computer, the USB 2.0 device is recognized incorrectly as a full-speed device instead of a high-speed device. Therefore, the transmission speed over the USB connection is significantly reduced.
This problem occurs occasionally.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB972485.