First of all, sorry! I don't know how I posted the thread twice. I was really troubled by the fact I had a problem with the update, a first in my Nisus life!
I suppose I can't suppress the other one, so Martin, when you read this, and I fervently hope you read this soon, do it for me, please!
I have tried all your suggestions. Updated from inside the application, from outside, said yes to restore windows, said no, Nisus 2.0.3 just won't open. I reloaded 2.0.2, and am working on that now, nothing I need is missing, but I am puzzled. This never happened to me before.
By the way, I am using a MacBook Air, 10.7.3, didn't go on to 10.7.4 because my most useful French dictionary had a problem with that, and I am hesitating to install 10.8 for the same reasons. And what if Nisus 2.0.2 didn't work with 10.8?
I need an idea other than the obvious, and I don't have it.

Martin? Are you there?