Hi,
Please check if the "USB selective suspends settings" option in the Power Options and "Allow the computer to turn off this device to save power" setting in Device Manager is Enabled.
For more information, please refer to the following article:
How to troubleshoot USB device problems that may occur after a PC that is running Windows 7 or Windows Vista resume from sleep or from hibernation
http://support.microsoft.com/kb/953367
Karen Hu
TechNet Community Support
