Steve et all-
No solution has been found yet, sad to say. Tried various USB ports on the T510, same results.
I had gone back to earlier driver version from the FTDI site with no change in performance or I should say lack thereof. BIOS was updated to most current again no joy in mudville.
I was able to read the printing on the chip in the RS 20-047 scanner interface, FT232BL. A google search identifies this as an FTDI chip and I have downloaded the uptodate drivers. The T510 machine through device manager in Win 7 sees the port and says it is functioning correctly.
I have ordered a different interface cable from a reputable source and will advise if it makes any difference.
Thanks for the comments and suggestions.