John and Don, thank you for the suggestions which I have followed.
In the customise keyboard list there is nothing in the list for 'edit reference point'. However I discovered it worked with alt +D whichever customised keyboard I used. The only time I can get D to show and refer to 'edit reference point' is in the Help menu keyboards shortcut list under current commands. But still not in the toolbars options keyboard list where I should be able to reset it. I've repaired and reloaded, but no change so I have to use the alt +D option.
I do have another problem now that when I select any object if I want to change its size in the edit size box at the bottom it will only change orthogonally in both dimensions ie if I change the x dimension the y dimension changes at the same time and vice versa. I can't find any setting that makes this happen, do you know if there is one? Thanks again, Sheila