Hi,
find attached very simple demo with NextGrid.
Try to hover mouse over any cell with truncated text, hint will appear correctly.
If you move mouse over another cell with truncated text, hint redraws again correctly,
however if you move mouse over empty part of grid, or outside of grid, hint remains on screen, doesn't hide.
To demonstrate how the hint is invoked and released in next grid, I add two buttons. First shows the hint, second should hide it.
You can download trial version of Next Grid at http://www.bergsoft.net/en-us/downloads.htm
Pavel