I have a weird behavior with TStringGrid in Delphi 7.
Delphi does not call the OnMouseUp event if a pop-up menu is associated to the grid. Basically, when the RMB is pressed, the pop of the menu somehow cancels/delays the OnMouseUp. Actually, to be 100% accurate, next time you push a mouse button the OnMouseUp is called twice – once for the current event, and once for the lost/delayed event.
This will screwup the entire logic of the program as unwanted code will be called next time when the user presses a mouse button.
I already took an approach somehow similar with the one described by Sertac: I just don’t use the PopupMenu property anymore to assign a pop-up menu to the grid. Instead, inside my grid (my grid is a heavily modified string grid derived from TStringGrid) I handle the mouse down event and display the pop-up the way I want AND do the extra processing I wanted to do BEFORE the menu pops.