It seems that tables cannot handle MBCS chars on Windows, there is some kind of problem in TStringGrid where it does not transfer the data after editing is done correctly.

I have tried to create a new form with one edit field just above the table cell being edited and using that TEdit object to edit the text. I have succeeded in doing that but this now means that you have to press Enter or F2 in order to start editing the cell contents. And you have to press Enter, F2 or Esc to finish editing. Esc - restores the value to the previous one.

Basically this is a stupid workaround, so I just had to put a lot of comments in code, explaining what is being done.