Thank you for that - the problem was (expensively) solved by buying the Vuescan Professional package. If I was a conspiracy theorist, I could easily be persuaded of 'possible interference', since the problems started when I downloaded their free (watermaked) version, while still using the PS Elements, Vuescan works very well and at £100 a licence, so it should !
I might have to do a little experimental loading on another machine, to see if the problem replicates
