In the TreeGrid demo at least under OS X in Chrome and Firefox:
dhtmlx.com/docs/products/dhtmlxT … ndex.shtml
If I double click on a cell in the “Ships in” column and use the mouse to scroll in the list that pops up, the selected item background changes from gray to blue. After this, arrow keys can be used to move between choices but pressing enter or esc does nothing, the selection popup doesn’t go away. The regular Grid does not have this problem.