new gnumeric
enter a long text in A1 (about as long as two columns are wide)
add any text in A2 and A3

Merge C2:C3 and format it for validation from the list with source A1:A3 having an in-cell-dropdown.

select the cell
click the drop down arrow and note that the menu incorrectly disappears as soon as the mouse is released.
If the mouse is dragged out of the menu before releasing it the menu stays open.


The problem occurs whenever the menu appears with a size and location that makes the menu overlap the trigger-arrow. This only happens if 
(a) the cell in question is a merged cell spanning at least two rows, since the menu appears just below the top row, and
(b) the menu content is longer than the cell in question.

This can clearly be fixed by ensuring that the menu always appears below the whole merged cell.

This is http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=660112