if you are using a Mac OSX as your Virtualbox host-system you might have had problems with the host not beeing able to pass the USB-Device to the (Windows or other) Guest.
1. shutdown the VM
2. plugin the USB Device
3. go to the settings of your VM and add a new Filter for the device (meaning: Virtualbox will try to catch access before OSX does… if OSX is first… the device is „locked“ and can not be mounted to the VM)
If you see the USB Symbol flashing… things should work.
I tested this with Windows 7 Ultimate (64Bits) and it gave me the „ding-dong-some-USB-Device-is-connected“ sound but did not display any Devices.
Under Windows XP SP3 it worked…. then the VM crashed.
it might help to uninstall Parallels and reboot the system.
It might also help to reinstall OSX from DVD/Internet.