Thank you for your most helpfull response.
As you say, Coomand Tab works fine, as does the two/three finger scroll. I hadn't been aware of these methods and had always previously used the Command H shortcut, which had always worked before the upgrade to Fusion V4.
In fact I've been using Command H so long that I can't even remember where I learnt about it, but I guess it must have been in some of the documentation I got when I first moved over to Macs and installed VMWare abut three years ago.
Anway, I'll use the othr methods from now on. Many thanks again for your advice - much appreciated.