Nikon Scan 4 no longer recognizes Coolscan V LS-50

I have been using this scanner on Windows XP regularly with both scan 4 for colour & vuescan for black & white & it has been working without fault. However when I turned it on yesterday it came up with unable to find active device even though the scanner is on & shows a steady green light. I have changed USB cables & re-installed scan 4, Even changed to another PC. It still won't work.

In anticipation you can help.

Cheers Newell