This may be a system thing. But I say several programs, including non-Apple apps, behaving in the Lion way. Maybe you need to add or change something to be 100% complaint with Lion?
The right one (grey,cannot be selected) should be changed to [Verwijder], because that button deletes the selected record:
Screen dump (deleted)
(The left button [Wis] (can be selected in this screen dump) only empties the entry.)
The two buttons on the lower left of the Transaction-tab, [Clear] and [Delete] are both translated as [Wis]. so now there are two buttons next to each other called [Wis].
Better would be [Wis] and [Verwijder].