try fixing it by disabling power management on the USB hub. This was from the HP site somewhere.
By default, Window XP tries to disable USB when the scanner is not used to save power. This simply does not work under many circumstances. The scanner fails to wake up when called. To fix this problem use the steps below:
Click Start, and right-click My Computer.
Click Properties, and click the Hardware tab
Click the Device Manager button.
Double-click the Universal Serial Bus controllers branch to expand it
Right-click USB Root Hub, and then click Properties.
Click the Power Management tab.
Remove the checkmark from Allow the computer to turn off this device to save power.
Click OK, and close Device Manager