Well, I'm still none the wiser as to why my registry changes won't 'stick', but even when they occasionally do, they don't seem to make any difference. But, thanks to suggestions made elsewhere, I have cured the problem using a different technique -and should anyone else ever wonder about the same problem, I have documented the cure here: http://diznix.com/2009/08/31/plsql-developer-in-wine/
