Update on this issue...
Well, this is a mystery as there is no consistancy.
This weekend I spent a lot of time working with the machine. The lost connection was happening frequently, usually on first run, usually when the spindle starts or is running for a short while. I moved the VFD about 10 inches away from the rest of the controller electronics and that seemed to fix the problem.
The next day, the problem comes right back again. I would power up the PC, start the MACH3 software, start the control electronics, start the VFD, and start the spindle - within a few minutes a lost connection.
I tried to revive a couple of older computers and install Mach on them, however, the one refused to boot up the other, with Windows Vista, powered up but was unable to run Mach3 without problems (DLL issue - yes, installed Mach3 Vista patch).
Finally, thinking back to answer about this problem reported elsewhere, someone mentioned to turn off power reduction on the USB ports which I had done but didn't seem to help. However, assuming low power could have been the problem, I added an AC powered USB hub between the computer and the UC100. I figure the AC powered USB Hub would have a consistant power level and perhaps eliminate that as an issue. So far, I have shut down and restarted the whole system about 10 to 15 times without a problem. I am still skeptical as I have tried other things that seemed to fix the problem only to have it come back again.
Chris D