DBGrid doesn't show selected value in lookup column until record posted

I use Client Dataset and DBGrid with a lookup field.
When I select a value from a lookup field inside the grid, the underlying
dataset properly changes current record, but the grid doesn't show the
selected value. It shows it when the record is posted. (Delphi 5.0, build
5.62)

This worked before until I recreated dataset and DBGrid.

Tom