The hover visual style is applied on non hovered cell in Windows 7 Theme. 

1. You should select a cell.
2. You should scroll the RadGridView with mouse wheel
3. You should hover the cell above the selected one.
4. You should select the cell below the current one.
5. You should scroll with mouse wheel.
6. After hovering the cells under the current cell several times, one of them will have gray background.