THE FOLLOWING from Dana DeLouis SOLVED THE PROBLEM. at least for the moment.
we will see when PC is restarted and all programs reloaded. A N Y W A Y - it
seems the following is working although the link assumed there was a Dword
value in registry set to "New Value #1" while in fact to correct the problem
I had also to cancel first the registry value "UndoHistory" that was present
also. then with no DWORD Values I was eventually able to follow the procedure
indicated in the link and edit the value itself. Thanks Dana!!!! :))

"Dana DeLouis" wrote:

> Perhaps check if anyone messed around with your Reg settings.
> Setting it to 0 disables Undo.
>
> How to modify the number of undo levels in Excel
> http://support.microsoft.com/kb/211922/en-us
>
> --
> HTH :>)
> Dana DeLouis
> Windows XP & Excel 2007

"Mostropovich" wrote:

> It happened all of a sudden:
> when I type something in a cell and move to another cell, the undo button
> greys and the undo function is therefore disabled.
> It never happened before, and I have no recollection of having modified
> settings. in this regard I could not find any setting to enable/disable the
> undo-redo buttons.
> can please somebody help/
> thanks