MouseUp event in TListView

I've recently upgraded to Delphi 5. This week I released a new version
of my c/s client software, and immidiately users started complainting,
that right clicking in the listviews no longer worked. And, much to my
surprise, TListview's OnMouseUp does no longer seem to work when the
cursor is over a ListItem. A "right-dbl-click" will trigger the
MouseUp event though. For now, I have worked around this, by moving
the code to MouseDown, which works fine, but does someone know of a
more lasting solution? Or perhaps I'm missing something alltogether
here, :-).