I have my pc (Win XP) connected directing to my Rio Central with the usb cable for direct sync (usb port #1 on the Rio). I was having problems with it and found out that it was a driver issue for the Rio Central with Win XP.

Just click on this site and update the Rio Central driver under system properties > hardware > device manager > usb controllers. The new driver file is RIOXDRV and you just need to update the driver (ie not install/reinstall emplode) : http://www.empeg.com/downloads/car-emplode-v2.00.zip

Hope that helps for anyone who was frustrated like me that I couldn't use the direct usb connection approach rather then using ethernet usb adapter or hpna.