Hi
Is the printer connected to a USB hub between the printer and the computer?
If it is, I suggest plugging the printer directly into the USB port to see if anything changes.
You might also try a different USB port.
Are you having any trouble with other USB devices?
I know you've stated you've tried the HP driver.
Just to make sure, here's a link to the 64bit drivers for that model that the Windows 7 Compatibility Center states is required for operation: