Have you plugged in the USB cable before you started UT? Are the drivers installed? (i.e. can you upload/download to/from this scanner using programming software?)
After you plug in the USB cable, and before you start UT, hit Windows+Break on your keyboard and find your way to the Device Manager. Open up "Ports (COM & LPT)" and see what you have there. You should have something in there which references a "USB Serial Port" (that's what mine says in Windows 7 for my PSR500). If you don't have any proper com ports showing, you may need the drivers to be reinstalled. Starrsoft has them on his page, if I recall correctly.