Hi Martin,
As you can see I actually registered this problem on the 4th May - so I have done quite a lot of restarting my computer since then. Actually it is so long ago I had actually forgotten I had left the post. Since then I added a studio monitor which seem to give a whole range of new unexpected problems - cubase not even seeing my UR22c - although all other programmes work with it fine. And cubase not registering midi in from my midi keyboards - despite them working fine with other programmes(Live, Logic, Studio One). after a number of hours of trying things it seemed that for some reason attaching the new monitor meant that I had to run the security hack outlined on the Cubase website again - and now it all seems to be working again