Hi Larry,
Your problem there is quite different: One of your USB peripherals is misbehaving and reporting an empty serial number. You should be able to find out which device it is by looking in your host's System Information tool, under Hardware> USB... just look for one with no Serial Number.
Remove whichever device is causing the problem, and you should be able to use Fusion 6. We have an update in the works that will allow Fusion to work with these devices.
So far, we've seen it with the Apogee Duet USB audio interface, a Zebra Thermal printer, and a handful of other devices. We'd be interested to hear which device is causing the problem for you.
Cheers,
--
Darius