as the mouse moves from one cell to another, it passes over the border (i believe the 1-pixel cellpadding that lets the outer div backcolor through).
anyway, the mouse shape changes from hand to pointer on that divider line and if the mouse stays on that position, the menu disapperas, as if the mouse was dragged out. any way this behavior can be fixed? at least the menu should remain up as long as the pointer is inside the block.
I'm running into the same issue, I too am looking for a solution to this problem.
you can disable gap between the table cells using 'table' key in template.js file. Border can be created by alternative ways, using inner HTML feature for example.