Hello Russ and thank you for responding to my question.
In fact the problem was me (nothing new there then) and my lack of familiarity with DW CS3 terminology.
The solution turned on like a light bulb this morning when I did something different. On my screen I had too many window tabs open (mine are on the RHS of the screen with the Files tab always open)
Once I closed the Files tab all was revealed as the say. Basically I had been obscuring that part of the Tabbed window that contained the CSS Styles/Current Properties because too may tabs were open and the Files tab content was taking the majority of the screen area.
I have been confusing the "Properties" pane that appears under the full page with the "Properties" pane that is part of CSS Styles/Current.
Not knowing there were two areas called "Properties" gave rise to my inability to select the correct one.
I guess this was an excellent example of "Most problems have simple orgins so most solutions are therefore simple"
Thanks again for your help - it helped me learn something new.