USB support in most virtualization solutions (VMWare, Virtual PC, VirtualBox etc) is either limited, unstable or does not exist. You can easily use USBDeviceShare to access the USB devices plugged in to the host machine from the virtual machine.
Install USBDeviceShare server in the host machine where USB devices are present. Share the devices which you need to access from the virtual machine. Now, install USBDeviceShare client in the virtual machine. Using the client connect to the server installed at host machine and plugin the devices which are shared there.
Download and try USBDeviceShare, our USB over network solution at http://www.sysnucleus.com/usbshare/usbshare_download.html . In case you need any assistance to setup USBDeviceShare or if you need any customizations, do not hesitate to contact us : http://www.sysnucleus.com/usbshare/support.html