guys, many thanks -
digging deeper I've found out these are problems
for other people too. But I am curious to know whether anybody on the December 2010 version of the 15.3 has a functioning pdfviewer.
Jackie, I was sure there was no point in putting in the Hacked version of Adobeviewer, as I thought the basic "engine" would be the same, but of course I was wrong

and the dictionary there works perfectly - or so it seems for the moment.
I should perhaps experiment with the first two beta versions to see what happens. Again, many thanks!
For future reference, and until we get a non beta version of 15

, I found
Kacir's beta testing sheet useful.